[Googi]

I've been using Paint Shop Pro 6 for over 7 years and it works great (although GIMP can sometimes be better for adding text to an image and is better at file compression). You probably won't be able to find many places still selling PSP6 though, and you'll want something newer if you want to do any kind of serious shading work (which you won't if you're just making Graal graphics).

Photoshop is the most popular but I find Paint Shop Pro to be more usable.