knittingzone.com has a pattern for felted baseball caps, but I think you have to buy it... :(
Also, my DH said that he would love a throw for when he's sitting on the couch... his mom made us one, but it's pink and blue... maybe one that's just for him would be nice?? with double stranded yarn and big needles, you can make them fairly quickly...
oh wait, didn't you say he's an artist?? How about a felted roll for his pens, pencils, brushes, etc??
I know I would love to have one of those, and have been wanting one for years.... It would work a lot better than most of the other organizers I have