Animated Crowd Scene

I would use Trapcode Particular to create the crowd. There's a very old tutorial that demonstrates the idea. It is a lot easier with the newer version of Particular.

You could also use Trapcode Form. 

Using a particle system to create the crowd is much easier than duplicating and randomizing your animated characters.

I've used this approach in the past:

1. Create a precomp that's the maximum height for each figure, and place each inside, next to each other, as if in a line
2. Create your main comp and add in the precomp.  Make it a 3D layer and position it.  
3. Duplicate this layer a bunch of times.  Swap the X scale on some
4. In the project panel, duplicate your precomp and shuffle the figures
5. Back in the main comp, parent all the precomps to a null.  Then select them all and duplicate them.
6. Whle all the duplicates are selected, hold ALT and drag in your duplicated precomp from the project panel.  This replaces all these copies with the alternative precomp.
7. Parent these to a new null layer and then move the null layer to place the crowds in a new space

By this point, AE might start to slow down a little, so start using the solo layer options to turn off the precomps until you're ready to render.

This approach gives you a festival vibe, but if you're after millions, then Mylenium's suggestion with something like fractal noise driving a displacement map will get you there.

I'm sure you can generate a million images with some AI tool and then just add some wobbly effects to create the illusion of motion. Even big movies use static photos for this stuff because after the first few rows you can barely discern anything. It's really not as complex as you may think.

Mylenium

Hi,

Maybe try Youtube for green screen Crowd scenes. Many are copyright free too.

Or search for a suitable template on Videohive.