What I think would be difficult isn't creating cute icons, but rather making a reasonable number of them that would fit into a user-friendly little key at the bottom of the rankings page. If you have 5 options for pk, 5 for rp, 10 for codebase, 5 for types of commercial... well, keep going and you've got one hell of a big key to scan through while you try to figure all the cute little icons out.