Needs to be compatible with CC-by 4.0
All kind of low-poly models that might make cool level-props (aka static map-models), similar to the tree or the crystals found in the game already.
Most will probably need to have a more fitting texture applied.
Please contribute as well.
I'll start:
http://www.blendswap.com/blends/view/71743
http://www.blendswap.com/blends/view/73246
http://www.blendswap.com/blends/view/69708
http://www.blendswap.com/blends/view/69666 (maybe)