Well, you can use an Ecosystem in Vue to create a crowd. If you want an animated crowd, I would suggest using alpha planes as mrsparky has mentioned.

Here's a tutorial on how to use After Effects to create a crowd.

http://www.dailymotion.com/video/x1k4az_tuto-after-effects-make-a-crowd_tech

The same principles can apply to Alpha Planes in Poser/Vue.

Posermocap - Motion Capture animations for Poser and Daz3D.