A while back I posted on the discussion board about how to achieve the cool effect of duplicating yourself many times in 1 photo, as in the picture below.
I'm putting a link back to the original post as I think people may still find it useful and it's gotten rather lost in the discussion area now.
To find out how to do this yourself check out the post How I Multiplied Myself
Hope you find it interesting! Look forward to seeing what you come up with.