There was someone who posted on the aircraft forum a month or so back that he was starting a custom decal shop. Someone also responded to his post that they had had some work done and it looked great. I thought I had a link to the site on my model links page, but I can't seem to find it.
Wheover it was did exactly what you wanted. They took your artwork and printed it. I'll see if I can find the link, but you might dig around in the old posts on the aircraft forum.
Here it is, I'm pretty sure: http://www.sparetimehobbies.com/