There are some posts in the Art Clay silver section, about making your own bezels. But I have to admit, that's not something I would want to do.
We do have some picture frame pendant/charms. They are not in our printed catalog, but they are available online. They are cast antiqued pewter-color.
One has a moon and star pattern on the frame; it is
#44-c456p. The other has butterflies and other bugs on the frame, and is
#44-c457p.
Another option is to make your own polymer clay frames. The "start-up" time, learning to make small canes to embellish them with, would be a bit slow, but once you got it down, each frame would be pretty quick.
You could make them as simple or fancy as you wanted.
I would tend to make a plain rectangular flat back, a bit bigger than your picture (enough bigger, so that you can securely glue the front and back of the frame together).
I realize those aren't QUITE the answers you were looking for, but I hope they help!
--Polly