hanging art

Hanging art at home when you have limited wall space and a lot of art is a challenge. I did some web research and found a few helpful articles on arranging art on a wall. Here is the best of what I've found:
http://www.rentaldecorating.com/0505walls/artwallarranging.htm

Also, I found different ways to support a changing art gallery without turning your walls into Swiss cheese. I am not sure what looks better though - hanging wires, or art on a shelf-ledge?

hanging wires: http://www.ashanging.com/?gclid=CLG7-5bj6JcCFQFvGgod6hQbDg

ledges: http://hollysview.blogspot.com/2008/07/art-ledges.html