Usually a year or two ahead of rule development I start painting figures and building terrain so that when we start to work on the rules, we have something with which to play test.
The vehicle in the foreground is a 10mm science fiction vehicle for scale. I recycled some packing material. One held a replacement GFE outlet, and the other held a bottle of some sort of goopy stuff I got from my wife. After painting them, I made some of the windows and doors in PowerPoint and printed them on label paper to stick on the buildings.