I'm currently trying to figure out how to have a dynamically changing shadow. Kind of like a shadow flicker.
This video is a perfect example http://www.youtube.com/watch?v=zG-MvUh9lHw
In my case I want to do it to this photo.
Any help is appreciated.
Not sure what you are trying to see there. It's just a light with animated intensity and the shadows naturally will follow it. Simply make everything a 3D layer, add a light, enable shadows. The flickering can easily be doen with a wiggle() expression or a few keyframes...