Well, I know who I'm giving Garfield an intro against when I work on him again (and a very insulting but SFW winquote), if I ever do so.
Anyway, since interests change, here's a fresh list of mine (will update this one if needed):
A decent Henry Stickmin: The sprites on the one that exists are decent enough, but the moveset is lackluster (and the edits don't help, based on the fact that it's based on BeanFan's stuff). With the series at an end now, I feel there is lots of material to gather for an actually good version.
More decent Skullgirls conversions: With how many good characters there are, it's a shame the whole cast didn't get this treatment. Joy Games' "conversions" of three of the characters feel like a total spit in the face compared to Filia and Squigly.
Bosses from River City Girls: I don't see a lot of conversions for non-fighting game bosses, and I figure why not, those ones have potential.
Characters from SEGA-era Puyo Puyo (post-7): Seeing the versions of Schezo and Draco gives me hope there'll be more good Puyo characters, but the version of Sig we have? Eh... (by post-7, I mean the designs from 20th or Tetris, it also wouldn't hurt to see a decent Compile-era Arle.)