you probably then already know how to make the billboard polygon, and are just looking for ways to make images of additional people.

do you live someone with places where crowds gather, like a football stadium? train station? take a camera and take pics. .... got a cell phone with a 2 MP cam?

You could also use a demo version of Quidam to create some variants of people and screenshot it. If there is a demo available these days. You probably won't notice the watermakrs on the people if you render them highres screenish and then resample down for the crowd size.

Whatever the origin of the people picture is, you'll want to grab a program to paint multiple instances of it in random sizes, color tints and other params,.... to plaster them into a crowd. Use the free Dogwaffle 1.2 to load an image into brush and paint it onto your composition.

Dogwaffle is on sale for renderosity members: www.thebest3d.com/renderosity

-Philip
thebest3d.com - beyond digital painting