A simple d-ring to work in conjunction with plasmaton's Cable Management Thingy http://www.thingiverse.com/thing:512163

I used simple picture hanging nails to hold it to the wall. It looks slightly deformed for 2 reasons. 1) one of the corners popped up while printing, but it still works. 2) the wall I have it mounted on is curved

minor edit:

raised the height of the mount so its easier to hammer a nail in.

added bevels to the inside corners to strengthen it up a little