Here's an example of some postal products being used to promote other items.
A group of pin up girls called the Pin Up Angels are selling their
posters and raising money to donate their photos and other gift items to troops overseas.
In a recent magazine article this Pin Up Angel was shown posing in front of a stack of APO/FPO priority boxes ready to ship to troops.
One thing for sure, the flat rate boxes are building an identity for USPS shipments. Easily recognized the world over.