There's a fair amount you can learn from a still photo for sure, but seeing the actual mechanisms in motion tells a whole lot more of the story. It's a lot easier to see what does what. This last week, after a hard days work in the shop, I took a few minutes and shot some video inside one of the heads I made.
This video shows the set up of what I like to call the Basic Four: moving mouth, side-to-side self-centering eyes, raising eyebrows and winkers. There are a variety of ways those animations can be made. This video demonstrates one way of doing these basic four mechanisms. Enjoy!