A service to make big (1mx2m or bigger) dense (1cm pitch) mazes. It would generate them pseudorandomly from seed, so you could re-order the same one if you wished and there would be also small a4 cheat sheet with path marked. You could order customized ones which from afar would have some image visible. I've even made one in local print shop, but just didn't even have time to test it with other people before I had too much work at other jobs.