When it came to hanging my many pictures in the hallway, I didn't want to punch nails all the way down my wall. So, I just used one anchor point at the very top and used a piece of wire (one of the strands from a CAT5E cable) and made these pieces to hang them serially, top to bottom, all the way to the floor.

Just thread the wire through the 3D printed hanger, making sure it goes down at least one of the circular channels before coming out the bottom end. For the last picture at the bottom, just bundle up the wire and press it flat behind the frame.

All you need is one hole at the top, however many pictures the wall height will allow, and each are perfectly centered right on top of one another.

So, make sure you share a pic if you happen to print one out (it makes my day each time someone prints something I designed) and be sure to peruse my other submissions which are almost as varied as they are many:

http://www.thingiverse.com/3E8/designs

Enjoy!