Or a Macarme/craft ring, I get mine from Hobby Lobby as Walmart seem to have stopped stocking them.
Fill it in, leave apertures, perch a bird or butterfly, whatever.
You will need to sand it for tinning if you want the patina to take.
This one is in my album but it wont hotlink as an image.
http://artisansofglass.com/index.php?action=mgallery;sa=media;id=668