I use my design program (Chief Architect x14)
I can generate walls with windows and doors, roof shingle patterns, the whole ball of wax. I used it to mock up the buildings in PawPaw that I've been building.
The 3D rendering capability adds shadows and reflections, which work nicely for back drop structures too.
Since I can print them out to scale, they make great templates for when it comes time to cut the styrene for the real deal.
I still have one more to go on this block...
Lee