Windows3.1 says:
What about a realistic track theme, where the track must be similar to a real road, closed course, or other structures that could be feasibly driven on?

I think the fact that TM2 is not like that is exactly what separates it from the 'realistic' racing games (dirt 3, NFS, etc) so with this theme you sort of kill off the TM spirit...

that being said it would be interesting to test your creative skills with something like this^^

Jet777 says:

Windows3.1 says:
What about a realistic track theme, where the track must be similar to a real road, closed course, or other structures that could be feasibly driven on?

I think the fact that TM2 is not like that is exactly what separates it from the 'realistic' racing games (dirt 3, NFS, etc) so with this theme you sort of kill off the TM spirit...

that being said it would be interesting to test your creative skills with something like this^^

To give an example, my old Beacon Island track was a "realistic" styled track, although it still had that Trackmania-esque feel to it (it did have a barrel roll about mid-way, but I justified it by giving it background as a giant fuel holding tank for the BC-304 from Stargate, which although isn't exactly real, it is feasible). That's what I mean by realistic tracks. You don't have to be 100% realistic, but no extreme stuff like floating platforms or giant loops that would have no chance of existing in real life.

Unrealistic stuff that would be ok:
Hitting a banked wall at full speed and riding it for a short time.
A three block long jump over a canyon.
Jumping from rooftop to rooftop of a city.
A GP track that crosses over itself several times.
A GP track with jumps.
A track built with narrow roads that leads onto a platform.
Off-road sections off of any surface.

Not ok:
Red boosts
Jumps that would require applying for a flight path.
An un-justified loop/wallride/barrel-roll/Immalman turn
Floating Platforms
Bridges that seem to go on endlessly
Jumping from high cliffs and landing on the ground

How about:

Spiral Theme
All turns, diagonals etc. must be in only one direction (left or right).

[EDIT]: This is about the direction of the car whilst driving. If you for example make a track where you only turn to the right, you are still allowed to use for instance the 1-block-sized left turns to create a diagonal, as long as the car can/would drive to the right. If unclear, please ask me and I'll post an image explaining the situation.

Tunnels
A car must be at least 50% of the track underground (inside the mountains, not in a box created with platform blocks etc).

Offroad
About 50-60% of the track has to be offroad. Also the thin road is road. Some scenery objects like pipes and hills are calculated as offroad.

Air time
Again, at least 40-50% of the track (in time) the car must be flying. No matter how or where - just flying.

-Use all sort of checkpoints-

wormi says:

Tunnels
A car must be at least 50% of the track underground (inside the mountains, not in a box created with platform blocks etc).

Offroad
About 50-60% of the track has to be offroad. Also the thin road is road. Some scenery objects like pipes and hills are calculated as offroad.

Air time
Again, at least 40-50% of the track (in time) the car must be flying. No matter how or where - just flying.

Seems like people are being conservative with their suggestions. How about changing all these to 90% instead?

Some other theme ideas:

vertical: map must be at least 3 times as tall (in blocks) as it is wide. In other words, if your map's top-down bounds are 10 x 8, then it must be 30 blocks tall. (max build height from canyon bottom to top of sky is 37 blocks)

map-in-a-box: map must fit within an 8x8x8 square (5x5x5?)

booster mania: the car must drive across a booster every 4th block

ups and downs: all blocks other than start/finish must be sloped or angled--no flat blocks or flat-to-slope transitions

top to bottom: track must start at the highest possible spot in the build area, and end at the lowest spot--AT also must be less than 1:00 (bottom to top would be even more challenging).

mix it up: every 4th block must be a road type transition (e.g. GP to narrow, narrow to canyon, canyon to cave, cave to platform, platform to tunnel, etc.)

round and round: track must be a 5-lap track, and AT must be less than 1:00

How about Use every road type in the game?
- GP
- platform
- ground roadmain
- elevated roadmain
- cliffside
- tunnel

This would teach people how to build tracks with more than just the same 2 road types out of 6.

Good ol' Endurance tracks.

How about a copycat theme?
Take your favorite TMO, TMS, TMN or TMUF track and convert it into a driveable canyon track?
(unfortunatly works only for people who have any old TM aswell.)

*to people who have built a track with old TM => a theme just for oldies => -1