Not exactly a screenshot, but a photo of a project I was working on. In addition to designing the main car frame, I also did the side frames, bulkheads, and link ‘n couplers. In other words, a kit.
All my design work was with FreeCAD 0.18 under Elementary OS Linux on a 9 years old Mac Mini.
I found that my 3D printer software, FlashPrint, likes it when I save my files in the .obj format.
I am currently working on assembling 11 “kits” of these cars for the ‘tree’ layout. I have posted photos with the @freecadnews Twitter feed.