Hi imonk,

I am a game developer who also happens to be an art hobbyist, so I always make art for my own game and therefore have to admit that I don't have any experience working with another artist. However, as a fellow artist myself, I think you should charge for the art. I don't understand why you would say something like "I don't have to do anything but the art." You shouldn't under-appreciate your skills. Art is one of the most important aspects of a game and sometimes could be even more time-consuming than programming. If you hire a programmer for your game, do you think you should pay them to work for you? If so, I don't see why a programmer shouldn't pay an artist to work on their game. If you really care less about getting paid, a possible solution I would suggest is to charge your client by each piece, instead of applying a minimum hourly wage.  Again I apologize for not being able to offer further insights since I've never worked with other artists, but I hope my thoughts can at least give you some ideas.