The VG Resource

Is it allowed to submit Fake Pokemon Sprites?
Can make into sprite sheet of rare pokemon front and back + non-rare front and back
can send drafts of pokemon in PNG image

No, fake Pokemon sprites -- or any sprites based on a character who has not appeared in a game -- will not be accepted for submission. If you read this page, you'll find out what can be submitted here, though.

This place doesn't accepts fanmade sprites unless they are god-like awesome, for what I've seen.
Considering the abysmal quality asociated with fanmade stuff, that's a good move IMO.