Here's a shot of the diorama I built for photographing my Warhammer 40K action figures. It can be seen out of focus and mostly in the dark, in the background of the last 2 photos I posted.
The bulk of it is made from foam core board. Some details are made from 2mm EVA foam, and the rest is parts I designed myself and 3d printed. I spent way too much time on details that are barely going be be seen in the back ground of a photo, but I had fun making it, and I learned a lot about designing and printing 3d parts along the way.