Just wanted to add there's a very nice larger scale, 1950s-60s single deck Greyhound bus originally from Dioramix, you might still find it on the Wayback Machine.
Minimodel.cz also had periodic theme design contests, and one included a very detailed 1:100 Scenicruiser - their PNG files usually scale up very well. If you can use that, scroll down this webpage:
http://soutez.minimodel.cz - 5.kolo