fixes

[TumeniNodes]

add default to your optional depends in mod.conf, and delete the depends.txt file
either your nodeboxes or textures are off, so be sure to take another look at them.

You also need to rename your texture file for the inv and weild to "beds_bunkbed_sides32x16.png"
The reason it was not showing is you had it as "bed_bunkbed_sides32x16.png"

Initially the beds were not even showing up for me, just their selection box, so I fixed up the code

I did not do a PR because I just took a quick look at the mod for you.

New code:

beds.register_bed("darkageobjects:bunk_bed", {
	description = "Bunk Bed",
	inventory_image = "beds_bunkbed_sides32x16.png",
	wield_image = "beds_bunkbed_sides32x16.png",
	tiles = {
		bottom = {
	--up (+Y), down (-Y), right (+X), left (-X), back (+Z), front (-Z).
			"beds_bunkbed_bottom_top.png",
			"beds_bunkbed_under.png",
			"beds_bunkbed_bottom_side.png",
			"beds_bunkbed_bottom_side.png^[transformFX",
			"beds_bunkbed_bottom_foot.png",
			"beds_bunkbed_bottom_head.png",
		},
		top = {
			"beds_bunkbed_top_top.png",
			"beds_bunkbed_under.png",
			"beds_bunkbed_top_side.png",
			"beds_bunkbed_top_side.png^[transformFX",
			"beds_bunkbed_top_foot.png",
			"beds_bunkbed_top_head.png",
		}
	},
	nodebox = {
		bottom = {
			{0.375, -0.375, -0.375, 0.5, -0.125, 0.5}, -- Brett_rechts
			{-0.5, -0.375, -0.375, -0.375, -0.125, 0.5}, -- Brett_links
			{-0.5, -0.5, -0.5, -0.375, 0.5, -0.375}, -- Pfosten_links
			{0.375, -0.5, -0.5, 0.5, 0.5, -0.375}, -- Pfosten_rechts
			{-0.5, -0.375, -0.5, 0.5, -0.125, -0.375}, -- Brett_vorne
			{-0.5, 0.25, -0.5, 0.5, 0.375, -0.375}, -- Leiste_vorn_oben
			{-0.5, 0, -0.5, 0.5, 0.125, -0.375}, -- Leiste_vorn_unten
			{-0.5, -0.375, -0.5, 0.5, -0.25, 0.5}, -- Boden
			{-0.375, -0.25, -0.375, 0.375, -0.125, 0.1875}, -- Kopfkissen
			{-0.375, -0.25, 0.1875, 0.375, -0.125, 0.5}, -- Kissen
		},
		top = {
			{-0.5, -0.5, 0.4375, -0.375, 0.1875, 0.5},
			{0.375, -0.5, 0.4375, 0.5, 0.1875, 0.5},
			{-0.5, 0, 0.4375, 0.5, 0.125, 0.5},
			{-0.5, -0.375, 0.4375, 0.5, -0.125, 0.5},
			{-0.5, -0.375, -0.5, -0.4375, -0.125, 0.5},
			{0.4375, -0.375, -0.5, 0.5, -0.125, 0.5},
			{-0.4375, -0.3125, -0.5, 0.4375, -0.0625, 0.4375},
		}
	},
	selectionbox = {-0.5, -0.5, -0.5, 0.5, 0.06, 1.5},

	recipe = {
		{"group:stick", "group:stick", "group:stick"},
		{"wool:white", "wool:white", "wool:white"},
		{"group:wood", "group:wood", "group:wood"},
	},
})

[Nordall]

I'm sorry, that I've forgotten to rename the .png. Now inv img and wielded img are shown. :)
But I still wonder, how to get this 3D effect. The inventory shows the bed from plain side.

[TumeniNodes]

The 3D image would need to be designed but I would not bother as it will not come out very good.
I feel the side view is the best way to go for these beds. It just needs a bit more to resemble a bunkbed