Rick, I have a steel mill 3d back drop building that is made from plywood with a styrene exterior glued on. You could do that with card stock too. I think the concrete and brick buildings look great in that environment. If you have not done it yet. Go on over to the 2 rail area on this forum and check out Roo's Action at the Steel Mill postings. Lots of great ideas there. Actually Roo has posted much good info over the years.