On the back of a magazine my husband gets were pictures of winning envelopes for the yearly contest of The Graceful Envelope. I didn't copy and paste any on my page because I didn't know if there would be a violation of copyright. Go to this web site: http://www.calligraphersguild.org/
So I checked out all the stamps available. You have to design an envelope to correspond with the stamp you are using and address it with calligraphy.
I am truly amazed at people's creativity!
While you're looking at the envelopes, check out all the information at the National Museum of Postal History ..... http://www.postalmuseum.si.edu/