As I said, I visited artists studios in Evergreen, CO, last weekend. One artist had a great wall for displaying her art. She had installed what appeared to be 1×4" planks in horizontal and vertical crossings. Across each was a series of nails and thumbtacks. These allow her to slap up a painting she's working on or display a whole bunch of them for visitors like me–without having a bunch of holes in the wall.
This isn't ideal for long-term installation of your artwork because the pattern of the boards interfere with an appreciation of the artwork. Might be better if the boards were painted the same color as the wall.
(By the way, I asked to get a picture of it, but she had no idea who I was and was suspicious of my intentions. I tried!)