GreetingStorm Live is a customisable viral video e-greeting toy, available in Facebook in various guises (e.g. Happy New Year), each with different movie templates to choose from.
Users can upload their face and change the greeting message.

The face photo will need to track the position/orientation of the character's head (as a flat quad), requiring it to transition/distort with every frame.  The positional data of each corner of the quad can be provided in an xml file output from any template Moviestorm movie (www.moviestorm.co.uk)

See http://apps.facebook.com/Photostorm_Halloween for a similar experience that involves 6 static photos superimposed onto a movie in Flash

It is reasonable to expect that the Greetingstorm can be built on the existing Photostorm code where possible