So I have had a fiddle with the Simply Adorned charms which are very cute. The Circle Charm fits the 1/2" circle punch (or should that be the other way around?)
I have photographed these at night so they are not the best quality...but you get the idea.
I stamped on Pretty In Pink using one of the flourishes from the Tiny Tags set. Over the top, using Concord Crush, I stamped a butterfly from Up In the Air, the hostess set in the current Summer Mini.
The other side of the charm....my initial is computer generated - I did not have a stamp sized for such a small space.
And of course, I can change the images whenever I want by just opening the charm and switching the design.