EDIT 10/19/14: I currently wont be able to do any skin conversions as I've gotten more busy with school. Sorry for those of you who's requests I was not able to complete, hopefully I'll be able to do conversions again in the future.
This is directly extracted and converted from the league of legends folder with no editing except for orientation and size of object. I did not create this and do not own it. This is just something I'm doing so other people that don't have the resources to do this may have access to the stl files.
How I extract them???
A lot of people seem to be interested so I'll just post here.
I extract the files from the league folder using a program called RAFmanager.
This program lets you get .skn files which need to be converted to .stl. This is done with Autodesk Maya using a Maya league of legends plugin and a stl conversion script.
After converting to stl, I fix the files using netfabb and reorient/resize them.
Scale however you'd like (as long as it fits on the platform!)
I have printed these with raft and support options checked.
I used 15% infill and 2 or 3 shells.