Running Home Assistant 0.114.4
edited to add some details.
Built a media player component today that selects from my ShieldTV as a cast-based media player, as an Android TV-based media_player, and my PS4. However, despite the fact that the universal player populates artwork just fine, the mini player does not show it:

For what it's worth, I am using a state-template to overwrite the state - entirely because depending on what app I'm using, the artwork/metadata fills out better on one vs the other method of accessing the Shield. I don't know why this is.
I did a close inspection on the code on the page and it doesn't seem to be rendering anything at all for the background-image in the web code:
<div class="mmp-player__core flex">
<div class="entity__icon">
<ha-icon></ha-icon>
</div>
<div class="entity__info">
<div class="entity__info__name">
Shield Media Player
</div>
<div class="entity__info__media" style="animation-duration: falses;">
<!----><span class="attr__media_title"><!---->Aladdin<!----></span><!----><span class="attr__app_name"><!---->VUDU<!----></span><!---->
</div>
</div>
<mmp-powerstrip>
</mmp-powerstrip>
</div>
<div class="mmp-player__adds">
<mmp-media-controls>
</mmp-media-controls>
<mmp-shortcuts>
</mmp-shortcuts>
<mmp-group-list>
</mmp-group-list>
</div>
vs mini-media-player when pointing at the shield's media_player directly:

Universal player config:
- platform: universal
name: Shield Media Player
state_template: >
{% if is_state('media_player.playstation_4','Playing') %}
{{ states('media_player.playstation_4') }}
{% elif is_state_attr('media_player.shieldtv', 'source','SageTV Miniclient') %}
{{ states('media_player.shieldtv') }}
{% else %}
{{ states('media_player.shield') }}
{% endif %}
children:
- media_player.shield
- media_player.shieldtv
- media_player.playstation_4
commands:
turn_on:
service: remote.turn_on
entity_id: remote.living_room
turn_off:
service: remote.turn_off
entity_id: remote.living_room
volume_up:
service: remote.send_command
entity_id: rremote.living_room
data:
device: B & K AV Receiver
command: VolumeUp
volume_down:
service: remote.send_command
entity_id: remote.living_room
data:
device: B & K AV Receiver
command: VolumeDown
State attributes:
volume_level: 1
is_volume_muted: false
media_content_id: Vudu
media_duration: 7678.25
media_position: 2067.314
media_position_updated_at: '2020-09-05T23:16:29.493170+00:00'
media_title: Aladdin
app_id: AndroidNativeApp
app_name: VUDU
active_child: media_player.shield
friendly_name: Shield Media Player
entity_picture: 'http://images2.vudu.com/poster2/1121066-338'
supported_features: 22463
Running Home Assistant 0.114.4
edited to add some details.
Built a media player component today that selects from my ShieldTV as a cast-based media player, as an Android TV-based media_player, and my PS4. However, despite the fact that the universal player populates artwork just fine, the mini player does not show it:
For what it's worth, I am using a state-template to overwrite the state - entirely because depending on what app I'm using, the artwork/metadata fills out better on one vs the other method of accessing the Shield. I don't know why this is.
I did a close inspection on the code on the page and it doesn't seem to be rendering anything at all for the background-image in the web code:
vs mini-media-player when pointing at the shield's media_player directly:

Universal player config:
State attributes: