To have pictures unfold down the screen as the camera follows them.
I know this is as simple as moving the anchor point to the bottom and rotating it, but I'm trying to figure out how to do it with expressions.
And it doesn't have to be pictures, comps would be good too. Somehow being able to use expressions so that they unfold down the screen. Much like if you were to take a stack of raffle tickets and let go they would fall end over end, that effect.
Expressions and expression controls can shortcut your rotation settings but Parenting is your friend in this exercise.
The problem is linking the precomps together so they remain attached to each other in a logical progression and unfold together, much like a wrist needs to be parented to an arm which is parented to the elbow, etc.
You can fake most of the unfolding if you don't need to simulate a stack of objects that has depth.
Expensive way to avoid learning expressions and parenting but, if you've got the money, Trapcode gets high marks around here.
I'm not at my AE machine for a few days but I'd approach the challenge starting with three simple layers, starting at the top, 1,2 and 3. Parent the top edge of 3 to the bottom edge of 2 and 2 to 1. You already know how to move the anchor points. Moving or rotating layer 1 will bring 2 and 3 along. Now try to rotate 3 about 100 degrees on the x axis so it sticks out, it's not going to fold up against 2 yet. Then rotate 2 on its x axis. 3 should follow logically. If it doesn't, you start over.
Once you hve the basic operation, you can duplicate the comp, make precomps of the photo layers so you can upstream effects, and experiment with turning them on or off only as they are needed.
Create a tall comp to hold your unfolding precomps. Bring this tall precomp into your main composition and add your lighting and camera rigs. Do not try to animate a camera in the tall comp. You want to move the tall comp up or down relative to the caemra instead of moving the camera. Add finesse and class by adding camera arcs and dollies.