If you've got a collection of clustered artwork that you'd like to visually unify, a simple solution is to paint the frames. A group of all white, all black, or all one-color frames will read more clearly as a whole, while a set of mix-n-match frames will create a more eclectic look...
These frames from the Picturewall Company create a very clean, streamlined arrangement. Black, white, and blonde are popular choices, but we'd also love to see a similar look with brightly colored frames. Although the color of your frame depends on your art, brightly colored frames can work well with neutral artwork. For instance, a set of black-and-white photographs would look incredible inside fire-engine red or lemon-yellow frames.
• Cheap Sources for Frames
• The Picture Wall Company
• How To: Hang Artwork in Clusters
• Good Questions: Clustered Frame Examples?
Photos: The Picturewall Company via Supermarket