Please forgive the extreme WIP nature of this post. If I wait until it is "done" to share, I'll never get there.
Here (if my attempt to link works) is my progess so far on a town on two (back to back) shelves. I have 16 inches on one side, 12 on the other, plus the depth of the wall.
....
I think I'm eventually going to raise the buildings over the track on both shelves -- unless I'm going to narrow the backs of the bigger modulars, 16 inches isn't much space for a modular, street, and train track, even if I set it up for street running. But oh my, the bricks. What you see on the one elevated side is not nearly as finished as I want it!