So... super strange. I added Sonic 2 to my library and it gave me the Sega Mega Drive and Genesis entry on my library... and it has changed the art work on every sega game in my library to the same artwork laid over to make it look like a random Sega system box art. Crazy taxi looks like a genesis game, Bayonetta has a Saturn layover, NiGHTS has a Game Gear layover...
It looks like this:
I literally have no idea how to undo this. I actually permanently removed the Genesis collection from my library via Steam Support, and rebooted steam but no effect. Anybody have any idea how to reset all the game tiles to their defaults? It's... super odd.