This is a remix of http://www.thingiverse.com/thing:97513 with the following changes:
- Reduced the height of the backplane, for quicker printing.
- Rounded corners looks nicer.
I also rotated the STL file so it can be directly imported into Slic3r.
Simply print (infill and material is not really critical, I used ABS with 25% infill), and then attach to wall with double-sided foam tape.