I know the theme's I suggest now have been mentioned before, and been done in earlier MTC's on TMX.
Island hopping:
- you can build a map on 3-5(or more) spaces X by X (example: 5x5)
(only scenery can be build outside these area's.)
- you have to cross at least 2 times from One "Island" to another one.
- Each island can only be used once.
edit: small mistake this was one of the last themes as fredair said
Build Inside or Outside of the given shape:
(just as we did on tmx the Build outside the sheep)
- A base map will be given for each enviroment.
- Your task is to build a map within the given shape or outside it (specified by the rules)
Hidden Cut's:
as The theme of the DTC (first unofficial mtc back on tmx)
- build a map in any style you wish.
- make an intended route and a route wich can be droven with the cut's you have hidden. (min 3 cut's)
- any mixure of cuts or none should be finishable without to much trouble.
(as long as you drive the map with the "cut" route you have to see the difference in time)