Only if you have PSP, JelZe. (to certain extent)

Additional links here.

Remember, tilesets are art. They require the same skills as art does. Good intentions don't make your tilesets nice. Experience, effort and talent do. If you lack one of those three, you can make do by having a lot of the other. If you put a lot of effort into a tileset, even if you lack experience, you could end up with something nice. But it's not just a flick of the magic wand.