Its possible that you can but just searching for good SF3 custom sprites for a character
if i'm not mistaken there are a few custom sf3 characters already released, like shoto Guile, Abigail, Dan, Gouken and Sheng long , if you want custom sprite sheets only then i think it wont be easy finding them because sf3 characters have too many frames/sprites to edit.
you could grab a sf3 sprite pack from the main site and try editing it if you want.