The transparency is messed up for the new ethan-gen2c avatar.
It's not obvious in Light Mode:
But it's pretty clear in Dark Mode:
I'm guessing transparency was used on a white background which coincided with the white used on Ethan's clothing. I'm not sure if other sprites have this problem, but this is just a heads up.
EDIT: So I went and tested every avatar listed on GitHub, and I found a few additional things (aside from sprites that are in the games but aren't on PS, but that's a different matter).
clerk-gen5bw doesn't have a sprite despite being listed in the array (it's counted as Invalid). (It's listed as clerk-boss which is inconsistent with the array)
hexmaniac-gen3 is just using the hexmaniac-gen3jp sprite moved left a few pixels (she should have irises in her eyeballs).
pokemonbreederm-gen3 and rocketgruntm-gen2 has a sprite that can be set as avatars but don't actually exist. (Pokemon breeder was just added; some people can see it, some can't.)
red-gen1 also has messed up transparency.