Nominations after having played all the user levels:
Here are my criteria for nominating a level:
2. It should be somewhat difficult, but fair.
3. A good design idea should eventually solve it with tweaking.
4. The scale should fit nicely with the others (not huge).
5. It should be different than the official levels in some meaningful way, especially in the problem it presents to the player.
6. It should present the player with a variety of options to solve it.
7. It should be an interesting level that I want to solve. This is a bit of an personal aesthetic thing. This includes the overall look of the level itself, realism such that there aren't random balls or sticks that defy gravity hanging permenantly in the air, and if possible a "wow" factor that just blows you away.
Cave Escape. http://FantasticContraption.com/?levelId=112
Already there are a wide variety of solutions to this puzzle. One piece designs, two piece designs, powered ramps, etc. It makes the machine go out and up, which none of the current levels do. Handling does to some degree, but this makes the machine reach up far more and gives a wall to use. Its a reasonable challenge (probably about 10-15 attempts for me). Its not vulnerable to clubbing or catapulting into submission, which I think is a positive since it forces even veterans to think a bit before building the exact same machine again. I think the level looks nice as well.
I'll take another look through, but on the first pass Cave Escape was the only obvious candidate. I think it could replace Up the Hump perhaps, which I'm not very fond of - or perhaps Around the Bend since Down Under is very similar but without the help from the side walls.