A few days ago I announced the competition to make a new YoFrankie level (for the next YoFrankie release) with 500 euro prize money divided between 1st, 2nd and 3rd.
A big advantage this has over other BGE competitions is that anyone who knows how to move objects about should be able to enter. (can use existing assets platforms, tree's etc And no logic bricks or scripting needed)
If your going to enter Id appreciate if you could post here, summarizing the kind of level your interested in making.
To start off you could open levels/level_selector.blend and modify the terrain, linking in more platforms and assets, I'll help out with more spesific questions on making levels (listen to blengine too!)
Since your not making your own game from scratch, this might not appeal to some....
On the other hand, a lot of the works alredy done, and I assure you testing a level with family/friends IS fun!