Wandering through Paul Race’s Family Garden Trains site, I stumbled across this page. Basically, it is printing photos of buildings on waterproof inkjet paper, then mounting it to a backing of some sort. It probably won’t satisfy the need for 3D buildings, but for something like Ray’s project, it will certainly serve until the building gets built. Additionally, it can fill in space for buildings that you just haven’t had time to build, yet. Another paper that isn’t mentioned is a 8.5" X 14" waterproof inkjet paper that I found in a backpacking store right next to the TOPO software. The stuff I found was marketed by NatGeo, but I’ll bet you can find the same stuff by Avery. Here is one building to wet your interest. I don’t think Paul will mind.
Evidence of photoshop magic is all over this.