This is an awesome idea use a thrift store frame behind a silhouette. Tutorial available from the bee and the bobbin.

This collection of silhouette faces is very cute and more vintage then modern especially with the pleat bottom chair and study lamp.

{Image from Valspar at Lowe's}

Now this collection of silhouette faces is more modern with a collection in the same frame, you could do this with your friends making different faces with props and then putting them in a long frame.