Sorry to bump this, but I've got some new information. First, I've found some graphics that I like, but 1) I don't know how to make up the missing animations that I'd need for SMBX and 2) There's more forms I would like to add. I know it's not much to go off, but it should give an idea of the graphic style I want the player character to follow. Found here.
I have also rethought the various abilities. Unless someone else wishes to help I should be able to work out the coding myself, however extra sprites will be required for things like attacking animations.
Will replace Toad (since I'm going to be scripting anyway and he's supposedly the easiest to work with. Axe functions similar to his boomerang anyway.)
OP will be updated with relevant information.