Storing & retrieving video camera frames in an ArrayList?

I'm trying to save frames from my MacBook's web camera to an Arraylist and then show three different images from the ArrayList.

The problem I'm having is that even though I'm pulling PImages from three different locations in the array (I think), I keep getting three of the exact same most recent images. Am I not referencing different locations in the ArrayList correctly?

Here's a stripped down version of the code on GitHub to show the problem I'm having:

Steve