dreadmullet says:
And the track has to be 5 minutes long.
Nah, in the end we would get less than 5 entries max and only 1 or 2 judges.
I suggest a theme where you should use all possible surfaces (offroad, RoadMain, GP, Arena, ArenaTunnel, RoadMainTunnel) with each surface being prominent in at least 3 blocks (not counting connection blocks) throughout the main road through the track.
The tracks that will come out will be creative since the authors are forced to use so many surfaces and they are forced to use them long enough that people notice.