I'm going to try something new: 3D maps. After a rough start, I think I'm getting the hang of it. I'm using basic foam board as a base. I found textured wallpaper to make stones out of. The biggest issue so far has been warping. It appears that I can correct that by simply painting the back of the board.
Painting it is easy. Black base paint, grey brush on the stone, and white highlights. Once everything is cut out, assembling and decorating moves along quickly.
So far, I've only done one floor section. I've started another with a slightly different approach. I'm wallpapering both sides. Theoretically, that will keep the water off the foamboard paper, which will prevent warping. Plus, since the whole thing will be modular, I can flip it for a different setting.