After measuring the opening of the frame, I (and by “I,” I mean my husband) cut a piece of 1/4″ smooth plywood.
Then, we fastened the wood into the frame, and painted it white (a nice backdrop for colorful jewelry). Another option would be to decoupage some decorative paper on it.
Small “s” hooks are the perfect size (and price) to use as the jewelry hangers (available at Lowes for $3-4/box). We pre-drilled, then screwed them in (and again, I use the term “we” loosely).
I spaced them evenly, but a haphazard approach would look just as nice. Also, I had considered buying a variety of decorative knobs, but went with these because of the great price.
(I reached back into the archives for this post; I originally posted this over at Blissfully Domestic, but wanted to highlight it again for my readers!)