I made a small room demonstrating the created illusion of people walking and dancing in a club.
You can't go in because the illusion only works from the outside. To explain this I uploaded a video.
http://www.youtube.com/watch?v=Kube9NVLBRwI looped a conveyor belt into a looping track with sprites on it.
I didn't get a chance to use this in a map, but I think somebody might be able to create a better version for their map.
The lighting could have been better along with other details but this is just to show you what is possible.
I replaced a looped ambient sound with some noise I created for the club music.