Okay, on the note of modding this game via altering it’s image files, I have managed to pull it off.

I found the image containing the joystick viewing icon usable in Training Mode, and altering its colour to be green instead of blue did actually make the colour in game be green.

I haven’t managed to find the background or player image files yet, but I believe that’s because they are encrypted within a group of .gfs files, which can be decrypted back into the original images via a software called Glarysoft.

This certainly isn’t the best place to be discussing game modding, but I’m mostly just testing the waters with this for now, and will update this comment with what I find in those .gfs files.

Edit: Okay, it seems those files aren’t actually openable with Glarysoft for some reason, and I can’t find any software that opens them.

This image did just get merged though, and I do actually have the higher res versions for all other characters, including Texas and Huggles (not sure why that’s there though…)
They’re also available in several different languages, including French, Spanish, Portuguese, Dutch, Korean, and Japanese.
Something weird though, is that all of the main 7 characters have a sheet in English that’s a .dds file of resolution 825x1050, though Texas, Huggles, and the All sheet have .png’s in English that are 1275x1650 in size.
Even weirder is that all other language versions of the sheets for the main 7 characters are in that higher 1275x1650 res for some reason.

I feel like those .dds files will get updated when the next update comes and Stronghoof gets added, as the devs’ll likely notice the discrepancy and fix it.