Here are a couple-three designs I put together for a small making event where I showed off my UM2 to some kids and their parents.  This project is more of a mash-up than my own design and was inspidered by the gears that I found at the following website http://www.thingiverse.com/thing:40410 that can be used to make gears that fit into Lego technics. I have a ton of lego technics and I really liked the idea that the motivated students to integrate their gear with their own legos. 

The design is fairly customizable. I recommend checking out my blog post if you want to see how I made the designs:

http://apprenticemaker.blogspot.com/2014/06/gears-with-logos.html

Also, all of the OpenScad and stl files can be found here on my gitlab account:

https://github.com/colbrydi/gear-givaways

Have fun.

- Dirk