I had the question where those paper cars are from so I'm gonna give you some links today from where I found some pretty cool stuff.
First there's a Blog named Papermau (link). Here you can find new paper stuff daily. Most isn't useful for tabletop but there are few good things from time to time. It's worth a look.
The other big site is Ninjatoes papercraft weblog (link). Similar to the blog above but with much more useful stuff like cars, busses etc etc. It has even a linkpage where you can select categories you want to search (link)
The cars I built are from a webpage from russia called Vladsity (link). I printed them in 80% size and that seems to fit perferct for 28mm models.
If you have some more links regarding that topic please share them with me in the coments below.