Maybe use an "official shape" that's different from the typical circle? No idea.
Badge No. 1
Dribbble - Badge by Nathan Romero
Mozilla Open Badges Blog — Introducing Open Badges 1.0. Today we’re extremely proud to release Mozilla Open Badges 1.0, an exciting new online standard to recognize and verify learning. Open Badges makes it easy to… earn badges for skills you learn online and offline give recognition for things you teach show your badges in the places that matter.