Are you only planning on editing the already existing overworld sprites? Just like you did with the eevee line? Or were you thinking of making and adding some that aren't in yet?Pretty much did them on the spot. I figured I'd share them here for others to enjoy. I want to edit more sprites, though I'm not sure which ones yet.
If only editing. Why not start with some of the wild alpha pokemon that can chase you in the overworld?
If you was thinking of making some from scratch though. Then yeah. Dunno. There's so many how do you just choose? I guess just start with some that you personally like. And work on from there?