Looks kind of vector/vexel-ish, but not that high quality (but I'm no expert on vectors/vexels, so don't take my word for it). I think you could do this in any kind of program, except maybe Paint. Umm.... Photoshop, Paint Shop Pro, probably GIMP (never used that either, so again, don't take my word on it).....
GIMP is free (you can get it
here), and there's a vexeling tutorial
here which I got from
this topic.
PS, PSP, and other graphic editing programs you have to buy........ or get it somehow *wink wink*