Check out the local "Stick and Staple" shop to find a graphic that you like, take a picture of it, and then replicate it or pay someone to replicate it for you... Seeing as they already have the colors matched up, you wont have to do any figuring...
I kinda like the Colored Rhyno-lining stuff. Never have to worry about painting the outside of the bus or scraping off the paint on trees, bushes, bicycles...