probably not the best way to capture stills and then re-animate them, but it can be done.
We do alot of this stuff for live "vj" apps.
I recommend actually capturing the webcam stream first using camtasia first, its by far the best for this kindda thing that i have found.
If you really have to use stills (captured frames) you will need an application to animate them in real time. It will probably be a waste of processor time, but check vjforums.com, there are plenty of links for software that would let you do this, for example visual jockey 3.5.