Initial play: This is just what I did while I was watching the tutorial. Doesn't look amazing by any stretch but thought I would include it to show progress.
First concept: Moved a little away from the cut-out and used the drop shadows to create a mountain of circles. Animated them in AFX because that was the idea I had after seeing Rich build up his pebble in the tutorial. I have some other imagery I would like to create which I will eventually update here. But for now, enjoy this circle animation. Unfortunately I haven't worked on it enough to make it endless, frames stop at the end and loses motion so I'll need to fix my keyframes up a little.