The British Monarchy has an official youtube channel! I just listened to 14 year old princess Elizabeth's very first BBC radio broadcast in 1940. The charming future Queen sent out a message of understanding and hope to the children of the world during World War II. These 4 little minutes of archived audio are more powerful than any history book and brought tears to my eyes!
This image isn't officially a postcard:) One could certainly print it out, stamp it, and send it out as one though!