Sorry for the late response.

The pink area on the texture, which should be transparent, doesn't seem to have any effect in the game.

Otherwise, the pink on the black-and-white layer appears as a greenish tint in the game, creating a rectangle that looks slightly out of place.

I’d classify this as ...

Since the revision of plants.lua in update 2.1.13, a portion of the 7th variant of the Teflilly plant is slightly visible to the right of the 6th variant.

https://i.postimg.cc/wTdZNxNC/Tefilly-variation-6.png

original line in plants.lua:

...
variations = gleba_tree_variations("teflilly", 10, 5 ...

I've noticed that several Gleba terrain textures have stripes of odd colors, which are also visible in the game when transitioning to water.
Also, the transition between the terrain textures and the terrain transition textures seems to be slightly offset in all cases.

lowland-dead-skin.png
has a ...

In the following image, “oil-ocean-deep” was used on the left side and “oil-ocean-deep-2” on the right. As you can see, “oil-ocean-deep” uses the corresponding oil-out-of-map transitions, while “oil-ocean-deep-2” uses the water-out-of-map textures.

https://i.postimg.cc/fb3prHRh/Example-out-of-map ...

There are 16 vulcanus-rock-medium textures, but only 14 are loaded (variation_count) in the "decoratives-vulcanus.lua".


...
layers =
{
util.sprite_load("__space-age__/graphics/decorative/vulcanus-rocks/vulcanus-rock-medium", { scale = 0.5, variation_count = 14,multiply_shift=0.5 ...

Under “Factorio\data\base\graphics\entity\assembling-machine-2”
there is an obsolete texture named “assembling-machine-2.png,”
and under “Factorio\data\base\graphics\entity\chemical-plant”
there is an obsolete texture named “chemical-plant.png.”

Neither of the two textures mentioned is used ...

There are 13 copper stromatolite and 13 iron stromatolite textures, but only 10 copper stromatolite and 11 iron stromatolite textures are loaded (variation_count) in the "decoratives-gleba.lua".

copper-stromatolite.lua:

return
{
width = 246,
height = 174,
shift = util.by_pixel( 5.5, 1.5 ...

There are pink artefacts in the first row of each of the following files: 'concrete.png' and 'stone-path.png' under 'data\base\graphics\terrain\water-transitions', and 'foundation.png' under 'data\space-age\graphics\terrain\water-transitions'.


https://i.postimg.cc/1t5kWgBd/concrete.png

https ...

In the tiles.lua under data/space-age/prototypes/tiles.lua is the integration of the foundation-transitions-lightmap.png missing in the "transitions between transitions" part of the foundation.

The newly added lightmap (foundation-transitions-lightmap.png) for the transitions isn't used anywhere ...

UPDATE [2.0.65]:

Update 2.0.65 has changed the situation.
Only the following two points remain from the original bug report:


missing stomper-corpse-effect-map (stomper/water_reflection/pictures)

stomper-corpse-1.png ---> ???
stomper-corpse-2.png ---> stomper-corpse-effect-map-1.png
stomper ...

The "stomper-corpse-1.png" texture does not match the "stomper-corpse-1.lua" and "stomper-corpse-1-mask.png".

stomper-corpse-1.png:
https://i.postimg.cc/bZG2Rj26/stomper-corpse-1.png

stomper-corpse-1-mask.png:
https://i.postimg.cc/JypV7SpL/stomper-corpse-1-mask.png

stomper-corpse-1.lua ...

The 63rd frame of the turbo transport belt frozen layer is identical to the first frame of the sequence in all 20 directions. Therefore, the 63rd frame was inserted incorrectly, and the actual 63rd frame is missing.

In terms of the error description, this corresponds to the following bug report ...

Hi, I am the author of the HD-Age mod.

In my image editing program, the alpha value is given in 8-bit from 0 to 255, and this value is 0 in the corresponding areas of the textures on the Alpha Channel. When transferred to the specification, 1/256 corresponds to this value. How is an alpha value of ...

The "fusion-generator-south-glow.png" still contains 6 frames and not 5 like the others.

To further specify the bug that still exists in 2.0.28:
The 63rd frame in the turbo transport belt frame sequence is identical to the first frame in the frame sequence for all 20 directions. Therefore, a wrong frame was inserted for the 63rd frame.

The Factorio\data\space-age\graphics\entity\stomper folder contains 70MB of unused textures from old Stomper versions.

The fourth variation of the huge Oxide and Promethium asteroids in the "asteroid.lua" are loaded into the variations array twice in a row and spawn more frequently than the others.