So, a fighting game in which the fighters are stages themselves for a fighting game? As Mr. Reeves would say; "Woah!"

Also, that'd actually be a pretty interesting idea for an actual game... the stage'd be shifting and moving about for one set/pair of fighters as the bigger pair (or one of them?) fights also. Now you gone and got my brain awhiring.

Depends on the style you're after.
I think Rick Griffin does adorable work but is a lil pricey, whereas a few more developing artists would be cheapter and have a distinctive feel to them. Personal recommendation for that would be  fiberopticfeline - especially if you are after a sketch style commission line up.