diff --git a/Image_Tag.php b/Image_Tag.php
index 705270e..78b833d 100644
--- a/Image_Tag.php
+++ b/Image_Tag.php
@@ -53,7 +53,8 @@ class Image_Tag implements ArrayAccess {
  	 * @param array $settings
  	 * @return Image_Tag
 	 */
-	static function create( $source, array $attributes = array(), array $settings = array() ) {
+	static function create( $source, $attributes = array(), array $settings = array() ) {
+		$attributes = ( array ) $attributes;
 
 		# If integer, create WordPress attachment image.
 		if ( is_int( $source ) )
@@ -580,8 +581,9 @@ function http( bool $force = false ) {
 	 * @uses Image_Tag::create()
 	 * @return Image_Tag_Picsum
 	 */
-	function picsum( array $attributes = array(), array $settings = array() ) {
-		$attributes = wp_parse_args( $attributes, $this->attributes );
+	function picsum( $attributes = array(), array $settings = array() ) {
+		$attributes = wp_parse_args( ( array ) $attributes, $this->attributes );
+		$settings = wp_parse_args( $settings, $this->settings );
 		$settings = wp_parse_args( $settings, array(
 			 'width' => $this->get_width(),
 			'height' => $this->get_height(),
@@ -600,8 +602,9 @@ function picsum( array $attributes = array(), array $settings = array() ) {
 	 * @uses Image_Tag::create()
 	 * @return Image_Tag_Placeholder
 	 */
-	function placeholder( array $attributes = array(), array $settings = array() ) {
-		$attributes = wp_parse_args( $attributes, $this->attributes );
+	function placeholder( $attributes = array(), array $settings = array() ) {
+		$attributes = wp_parse_args( ( array ) $attributes, $this->attributes );
+		$settings = wp_parse_args( $settings, $this->settings );
 		$settings = wp_parse_args( $settings, array(
 			 'width' => $this->get_width(),
 			'height' => $this->get_height(),
@@ -618,14 +621,20 @@ function placeholder( array $attributes = array(), array $settings = array() ) {
 	 * @uses Image_Tag::create()
 	 * @return Image_Tag_JoeSchmoe
 	 */
-	function joeschmoe( array $attributes = array(), array $settings = array() ) {
+	function joeschmoe( $attributes = array(), array $settings = array() ) {
+		$settings = wp_parse_args( $settings, $this->settings );
+		$settings = wp_parse_args( $settings, array(
+			 'width' => $this->get_width(),
+			'height' => $this->get_height(),
+		) );
+
 		$_attributes = $this->attributes;
 
 		unset(
 			$_attributes['srcset']
 		);
 
-		$attributes = wp_parse_args( $attributes, $_attributes );
+		$attributes = wp_parse_args( ( array ) $attributes, $_attributes );
 
 		return Image_Tag::create( 'joeschmoe', $attributes, $settings );
 	}
diff --git a/image_tags/Image_Tag_JoeSchmoe.php b/image_tags/Image_Tag_JoeSchmoe.php
index 5d3ab99..294851c 100644
--- a/image_tags/Image_Tag_JoeSchmoe.php
+++ b/image_tags/Image_Tag_JoeSchmoe.php
@@ -88,7 +88,7 @@ function get_ratio() {
 	 * @param array $settings
 	 * @return $this
 	 */
-	function joeschmoe( array $attributes = array(), array $settings = array() ) {
+	function joeschmoe( $attributes = array(), array $settings = array() ) {
 		return $this;
 	}
 
diff --git a/image_tags/Image_Tag_Picsum.php b/image_tags/Image_Tag_Picsum.php
index ad0abbb..0209ffa 100644
--- a/image_tags/Image_Tag_Picsum.php
+++ b/image_tags/Image_Tag_Picsum.php
@@ -93,7 +93,8 @@ function get_src_attribute() {
 		if ( !empty( $this->get_setting( 'grayscale' ) ) )
 			$src = add_query_arg( 'grayscale', 1, $src );
 
-		return $src;
+		# If there's a trailing slash, an extra redirect is made.
+		return untrailingslashit( $src );
 	}
 
 	/**
@@ -254,7 +255,7 @@ function details() {
 	 * @param array $settings
 	 * @return $this
 	 */
-	function picsum( array $attributes = array(), array $settings = array() ) {
+	function picsum( $attributes = array(), array $settings = array() ) {
 		return $this;
 	}
 
diff --git a/image_tags/Image_Tag_Placeholder.php b/image_tags/Image_Tag_Placeholder.php
index b2a44aa..4a92fd3 100644
--- a/image_tags/Image_Tag_Placeholder.php
+++ b/image_tags/Image_Tag_Placeholder.php
@@ -183,7 +183,7 @@ function get_height_setting() {
 	 * @param array $settings
 	 * @return $this
 	 */
-	function placeholder( array $attributes = array(), array $settings = array() ) {
+	function placeholder( $attributes = array(), array $settings = array() ) {
 		return $this;
 	}
 
diff --git a/image_tags/Image_Tag_WP_Attachment.php b/image_tags/Image_Tag_WP_Attachment.php
index 66dcb5e..9122324 100644
--- a/image_tags/Image_Tag_WP_Attachment.php
+++ b/image_tags/Image_Tag_WP_Attachment.php
@@ -93,7 +93,8 @@ function __toString() {
 	 */
 	function is_valid() {
 		return (
-			'attachment' === get_post_type( $this->attachment_id )
+			!empty( $this->attachment_id )
+			&& 'attachment' === get_post_type( $this->attachment_id )
 			&& wp_attachment_is_image( $this->attachment_id )
 		);
 	}
@@ -180,24 +181,28 @@ protected function set_image_sizes_setting( $image_sizes ) {
 	 *
 	 * @uses Image_Tag::get_width()
 	 * @uses $this->is_valid()
-	 * @uses $this->get_setting()
 	 * @uses $this->get_versions()
+	 * @uses $this->get_setting()
 	 * @return int
 	 */
 	function get_width() {
 		if ( !empty( parent::get_width() ) )
 			return parent::get_width();
 
-		if ( !$this->is_valid() ) {
-			$image_sizes = $this->get_setting( 'image-sizes' );
+		if ( $this->is_valid() )
+			return ( int ) $this->get_versions()['__largest']->width;
+
+		$image_sizes = $this->get_setting( 'image-sizes' );
+		$sizes = wp_get_registered_image_subsizes();
+
+		while ( !empty( $image_sizes ) ) {
 			$image_size = array_pop( $image_sizes );
-			$sizes = wp_get_registered_image_subsizes();
 
 			if ( isset( $sizes[$image_size] ) )
 				return ( int ) $sizes[$image_size]['width'];
 		}
 
-		return ( int ) $this->get_versions()['__largest']->width;
+		return 0;
 	}
 
 	/**
@@ -205,24 +210,28 @@ function get_width() {
 	 *
 	 * @uses Image_Tag::get_height()
 	 * @uses $this->is_valid()
-	 * @uses $this->get_setting()
 	 * @uses $this->get_versions()
+	 * @uses $this->get_setting()
 	 * @return int
 	 */
 	function get_height() {
 		if ( !empty( parent::get_height() ) )
 			return parent::get_height();
 
-		if ( !$this->is_valid() ) {
-			$image_sizes = $this->get_setting( 'image-sizes' );
+		if ( $this->is_valid() )
+			return ( int ) $this->get_versions()['__largest']->height;
+
+		$image_sizes = $this->get_setting( 'image-sizes' );
+		$sizes = wp_get_registered_image_subsizes();
+
+		while ( !empty( $image_sizes ) ) {
 			$image_size = array_pop( $image_sizes );
-			$sizes = wp_get_registered_image_subsizes();
 
 			if ( isset( $sizes[$image_size] ) )
 				return ( int ) $sizes[$image_size]['height'];
 		}
 
-		return ( int ) $this->get_versions()['__largest']->height;
+		return 0;
 	}
 
 	/**
@@ -253,6 +262,9 @@ function get_versions() {
 		if ( !empty( array_filter( $this->versions ) ) )
 			return $this->versions;
 
+		if ( !$this->is_valid() )
+			return array();
+
 		$image_sizes = $this->get_setting( 'image-sizes' );
 		$largest  = null;
 		$smallest = null;
@@ -383,7 +395,7 @@ function get_colors( int $count = 3, bool $force = false ) {
 	 * @uses Image_Tag_Picsum->add_srcset()
 	 * @return Image_Tag_Picsum
 	 */
-	function picsum( array $attributes = array(), array $settings = array() ) {
+	function picsum( $attributes = array(), array $settings = array() ) {
 		$picsum = parent::picsum( $attributes, $settings );
 
 		if (
@@ -421,7 +433,7 @@ function picsum( array $attributes = array(), array $settings = array() ) {
 	 * @uses Image_Tag_Placeholder->add_srcset()
 	 * @return Image_Tag_Placeholder
 	 */
-	function placeholder( array $attributes = array(), array $settings = array() ) {
+	function placeholder( $attributes = array(), array $settings = array() ) {
 		$placeholder = parent::placeholder( $attributes, $settings );
 
 		if (
@@ -466,7 +478,8 @@ static function lqip_transient_key( int $attachment_id ) {
 	 *
 	 * @todo check if LQIP file already exists
 	 */
-	function lqip( array $attributes = array(), array $settings = array() ) {
+	function lqip( $attributes = array(), array $settings = array() ) {
+		$attributes = ( array ) $attributes;
 		$_attributes = $this->attributes;
 
 		unset(
diff --git a/tests/test-picsum.php b/tests/test-picsum.php
index 8b5238f..7237984 100644
--- a/tests/test-picsum.php
+++ b/tests/test-picsum.php
@@ -11,7 +11,12 @@ function test_base_source() {
 		$img = Image_Tag::create( 'picsum' );
 
 		$this->assertEquals( 'https://picsum.photos/', Image_Tag_Picsum::BASE_URL );
-		$this->assertEquals( Image_Tag_Picsum::BASE_URL, $img->get_attribute( 'src' ) );
+		$this->assertEquals( untrailingslashit( Image_Tag_Picsum::BASE_URL ), $img->get_attribute( 'src' ) );
+	}
+
+	function test_src_attribute() {
+		$img = Image_Tag::create( 'picsum' );
+		$this->assertEquals( untrailingslashit( Image_Tag_Picsum::BASE_URL ), $img->get_attribute( 'src' ) );
 	}
 
 	function test_blur_setting() {
@@ -56,7 +61,7 @@ function test_seed_setting() {
 		$seed = urlencode( sanitize_title_with_dashes( $seed ) );
 
 		$this->assertEquals( $seed, $img->get_setting( 'seed' ) );
-		$this->assertContains( 'seed/' . $seed . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( 'seed/' . $seed, $img->get_attribute( 'src' ) );
 	}
 
 	/**
@@ -82,7 +87,7 @@ function test_width() {
 
 		$this->assertEquals( $width, $img->get_setting(   'width' ) );
 		$this->assertEquals( $width, $img->get_attribute( 'width' ) );
-		$this->assertContains( '/' . $width . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( '/' . $width, $img->get_attribute( 'src' ) );
 
 		$img = Image_Tag::create( 'picsum', array(
 			'width' => $width,
@@ -90,7 +95,7 @@ function test_width() {
 
 		$this->assertEquals( $width, $img->get_setting(   'width' ) );
 		$this->assertEquals( $width, $img->get_attribute( 'width' ) );
-		$this->assertContains( '/' . $width . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( '/' . $width, $img->get_attribute( 'src' ) );
 
 		$img = Image_Tag::create( 'picsum', array(
 			'width' => $width,
@@ -100,7 +105,7 @@ function test_width() {
 
 		$this->assertEquals( $width,     $img->get_attribute( 'width' ) );
 		$this->assertEquals( $width * 2, $img->get_setting(   'width' ) );
-		$this->assertContains( '/' . ( $width * 2 ) . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( '/' . ( $width * 2 ), $img->get_attribute( 'src' ) );
 		$this->assertContains( 'width="' . $width . '"', $img->__toString() );
 
 		$img = Image_Tag::create( 'picsum' );
@@ -134,7 +139,7 @@ function test_height() {
 		$this->assertEquals(  $width, $img->get_attribute(  'width' ) );
 		$this->assertEquals( $height, $img->get_setting(   'height' ) );
 		$this->assertEquals( $height, $img->get_attribute( 'height' ) );
-		$this->assertContains( '/' . $width . '/' . $height . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( '/' . $width . '/' . $height, $img->get_attribute( 'src' ) );
 
 		$img = Image_Tag::create( 'picsum', array(
 			 'width' => $width,
@@ -145,7 +150,7 @@ function test_height() {
 		$this->assertEquals(  $width, $img->get_attribute(  'width' ) );
 		$this->assertEquals( $height, $img->get_setting(   'height' ) );
 		$this->assertEquals( $height, $img->get_attribute( 'height' ) );
-		$this->assertContains( '/' . $width . '/' . $height . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( '/' . $width . '/' . $height, $img->get_attribute( 'src' ) );
 
 		$img = Image_Tag::create( 'picsum', array(
 			 'width' => $width,
@@ -159,7 +164,7 @@ function test_height() {
 		$this->assertEquals( 2 * $height, $img->get_setting(   'height' ) );
 		$this->assertEquals(  $width, $img->get_attribute(  'width' ) );
 		$this->assertEquals( $height, $img->get_attribute( 'height' ) );
-		$this->assertContains( '/' . ( 2 * $width ) . '/' . ( 2 * $height ) . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( '/' . ( 2 * $width ) . '/' . ( 2 * $height ), $img->get_attribute( 'src' ) );
 		$this->assertContains( 'width="' . $width . '" height="' . $height . '"', $img->__toString() );
 	}
 
@@ -206,7 +211,7 @@ function test_random_setting() {
 	 * @group http
 	 */
 	function test_random_http() {
-		$img = Image_Tag::create( 'picsum', array(), array(
+		$img = Image_Tag::create( 'picsum', null, array(
 			'random' => true,
 			'width' => 200,
 		) );
@@ -241,7 +246,7 @@ function test_image_id_setting() {
 		) );
 
 		$this->assertEquals( $image_id, $img->get_setting( 'image_id' ) );
-		$this->assertContains( '/id/' . $image_id . '/', $img->get_attribute( 'src' ) );
+		$this->assertContains( '/id/' . $image_id, $img->get_attribute( 'src' ) );
 	}
 
 	/**
diff --git a/tests/test-wp-attachment.php b/tests/test-wp-attachment.php
index f05dc06..c196083 100644
--- a/tests/test-wp-attachment.php
+++ b/tests/test-wp-attachment.php
@@ -172,7 +172,7 @@ function test_ratio() {
 	 * @group picsum
 	 */
 	function test_picsum() {
-		$image_sizes = array( 'medium', 'large' );
+		$image_sizes = array( 'medium', 'large', 'full' );
 		$img = Image_Tag::create( static::$attachment_id, array(), array( 'image-sizes' => $image_sizes ) );
 		$picsum = $img->picsum();
 
@@ -183,9 +183,10 @@ function test_picsum() {
 	/**
 	 * @group _placeholder
 	 * @group picsum
+	 * @group http
 	 */
 	function test_picsum_from_invalid() {
-		$image_sizes = array( 'medium', 'large' );
+		$image_sizes = array( 'medium', 'large', 'full' );
 		$img = Image_Tag::create( 0, array(), array( 'image-sizes' => $image_sizes ) );
 		$picsum = $img->picsum();
 
@@ -201,6 +202,20 @@ function test_picsum_from_invalid() {
 		) );
 		$this->assertEquals( 160, $picsum->get_attribute( 'width' ) );
 		$this->assertEquals(  90, $picsum->get_attribute( 'height' ) );
+
+		$this->assertEquals( 'image/jpeg', wp_remote_retrieve_header( $picsum->http(), 'content-type' ) );
+
+		$img = Image_Tag::create( 0, null, array(
+			'image-sizes' => array( 'full' ),
+			'width' => 1600,
+			'height' => 900,
+		) );
+		$this->assertEquals( 1600, $img->get_setting(  'width' ) );
+		$this->assertEquals(  900, $img->get_setting( 'height' ) );
+
+		$picsum = $img->picsum();
+		$this->assertEquals( 1600, $picsum->get_setting(  'width' ) );
+		$this->assertEquals(  900, $picsum->get_setting( 'height' ) );
 	}
 
 	/**
@@ -208,7 +223,7 @@ function test_picsum_from_invalid() {
 	 * @group placeholder
 	 */
 	function test_placeholder() {
-		$image_sizes = array( 'medium', 'large' );
+		$image_sizes = array( 'medium', 'large', 'full' );
 		$img = Image_Tag::create( static::$attachment_id, array(), array( 'image-sizes' => $image_sizes ) );
 		$placeholder = $img->placeholder();
 
@@ -219,17 +234,32 @@ function test_placeholder() {
 	/**
 	 * @group _placeholder
 	 * @group placeholder
+	 * @group http
 	 */
 	function test_placeholder_from_invalid() {
-		$image_sizes = array( 'medium', 'large' );
+		$image_sizes = array( 'medium', 'large', 'full' );
 		$img = Image_Tag::create( 0, array(), array( 'image-sizes' => $image_sizes ) );
 		$placeholder = $img->placeholder();
 
 		$this->assertInstanceOf( 'Image_Tag_Placeholder', $placeholder );
-		$this->assertEquals( 1024, $placeholder->get_attribute( 'width' ) );
+		$this->assertEquals( 1024, $placeholder->get_attribute(  'width' ) );
 		$this->assertEquals( 1024, $placeholder->get_attribute( 'height' ) );
 		$this->assertNotEmpty( $placeholder->get_attribute( 'src' ) );
 		$this->assertEmpty( $placeholder['srcset'] );
+
+		$this->assertEquals( 'image/png', wp_remote_retrieve_header( $placeholder->http(), 'content-type' ) );
+
+		$img = Image_Tag::create( 0, null, array(
+			'image-sizes' => array( 'full' ),
+			'width' => 1600,
+			'height' => 900,
+		) );
+		$this->assertEquals( 1600, $img->get_setting(  'width' ) );
+		$this->assertEquals(  900, $img->get_setting( 'height' ) );
+
+		$placeholder = $img->picsum();
+		$this->assertEquals( 1600, $placeholder->get_setting(  'width' ) );
+		$this->assertEquals(  900, $placeholder->get_setting( 'height' ) );
 	}
 
 	/**
@@ -237,7 +267,7 @@ function test_placeholder_from_invalid() {
 	 * @group joeschmoe
 	 */
 	function test_joeschmoe() {
-		$img = Image_Tag::create( static::$attachment_id, array(), array( 'image-sizes' => array( 'medium', 'large' ) ) );
+		$img = Image_Tag::create( static::$attachment_id, array(), array( 'image-sizes' => array( 'medium', 'large', 'full' ) ) );
 		$joeschmoe = $img->joeschmoe();
 
 		$this->assertInstanceOf( 'Image_Tag_JoeSchmoe', $joeschmoe );
@@ -247,13 +277,15 @@ function test_joeschmoe() {
 	/**
 	 * @group _placeholder
 	 * @group joeschmoe
+	 * @group http
 	 */
 	function test_joeschmoe_from_invalid() {
-		$img = Image_Tag::create( 0, array(), array( 'image-sizes' => array( 'medium', 'large' ) ) );
+		$img = Image_Tag::create( 0, array(), array( 'image-sizes' => array( 'medium', 'large', 'full' ) ) );
 		$joeschmoe = $img->joeschmoe();
 
 		$this->assertInstanceOf( 'Image_Tag_JoeSchmoe', $joeschmoe );
 		$this->assertNotEmpty( $joeschmoe->get_attribute( 'src' ) );
+		$this->assertEquals( 'image/svg+xml; charset=utf-8', wp_remote_retrieve_header( $joeschmoe->http(), 'content-type' ) );
 	}
 
 	function test_colors() {
diff --git a/tests/test-wp-theme.php b/tests/test-wp-theme.php
index 9243ac6..17cc4e1 100644
--- a/tests/test-wp-theme.php
+++ b/tests/test-wp-theme.php
@@ -36,6 +36,7 @@ function test_picsum() {
 	/**
 	 * @group _placeholder
 	 * @group picsum
+	 * @group http
 	 */
 	function test_picsum_from_invalid() {
 		$img = Image_Tag::create( 'image-does-not-exist.jpg' );
@@ -47,6 +48,20 @@ function test_picsum_from_invalid() {
 		) );
 		$this->assertEquals( 160, $picsum->get_attribute( 'width' ) );
 		$this->assertEquals(  90, $picsum->get_attribute( 'height' ) );
+
+		$this->assertEquals( 'image/jpeg', wp_remote_retrieve_header( $picsum->http(), 'content-type' ) );
+
+		$img = Image_Tag::create( 0, null, array(
+			'image-sizes' => array( 'full' ),
+			'width' => 1600,
+			'height' => 900,
+		) );
+		$this->assertEquals( 1600, $img->get_setting(  'width' ) );
+		$this->assertEquals(  900, $img->get_setting( 'height' ) );
+
+		$picsum = $img->picsum();
+		$this->assertEquals( 1600, $picsum->get_setting(  'width' ) );
+		$this->assertEquals(  900, $picsum->get_setting( 'height' ) );
 	}
 
 	/**
@@ -61,6 +76,7 @@ function test_placeholder() {
 	/**
 	 * @group _placeholder
 	 * @group placeholder
+	 * @group http
 	 */
 	function test_placeholder_from_invalid() {
 		$img = Image_Tag::create( 'image-does-not-exist.jpg' );
@@ -72,6 +88,20 @@ function test_placeholder_from_invalid() {
 		) );
 		$this->assertEquals( 160, $placeholder->get_attribute( 'width' ) );
 		$this->assertEquals(  90, $placeholder->get_attribute( 'height' ) );
+
+		$this->assertEquals( 'image/png', wp_remote_retrieve_header( $placeholder->http(), 'content-type' ) );
+
+		$img = Image_Tag::create( 0, null, array(
+			'image-sizes' => array( 'full' ),
+			'width' => 1600,
+			'height' => 900,
+		) );
+		$this->assertEquals( 1600, $img->get_setting(  'width' ) );
+		$this->assertEquals(  900, $img->get_setting( 'height' ) );
+
+		$placeholder = $img->placeholder();
+		$this->assertEquals( 1600, $placeholder->get_setting(  'width' ) );
+		$this->assertEquals(  900, $placeholder->get_setting( 'height' ) );
 	}
 
 	/**
@@ -86,10 +116,13 @@ function test_joeschmoe() {
 	/**
 	 * @group _placeholder
 	 * @group joeschmoe
+	 * @group http
 	 */
 	function test_joeschmoe_from_invalid() {
 		$img = Image_Tag::create( 'image-does-not-exist.jpg' );
+
 		$this->assertInstanceOf( 'Image_Tag_JoeSchmoe', $img->joeschmoe() );
+		$this->assertEquals( 'image/svg+xml; charset=utf-8', wp_remote_retrieve_header( $img->joeschmoe()->http(), 'content-type' ) );
 	}
 
 	function test_colors() {