Although this may not be of much help to you. When I went to the Louisville Hotrod show a few weeks ago in their new products area they had a program that was around $50 or so that you can color your car with and add graphics to. I wish I could remember the name of it, but maybe on of the other guys here that went saw it and can remember the name of it.
It may not even be out on the market yet though, but was just a thought. Sorry I can not help you anymore than that.