I am coming in late here, but I just bought this system which is simple to use and flexible. I am very happy with it.

In Australia, it is the system used by most art galleries.
I think this an American based company.

http://www.thegallerysystem.com/

Tricia, thank you for posting this system, it looks very practical. I've been looking for something that will work in my (future) home studio, I will hang on to this for future reference. Thanks!