can you make folder icons show folder contents?

is it possible to do on a mac?

ok, a bit of back story

The other day while I was around at a friends place, we where on his computer, and as I was watching him struggling to get vista to do what he wanted and wondering why he wouldn't just try mac like I have suggested so many times before, I actually did notice a little feature of vista that I liked, the icons of all his folders, showed in the icon, the contents of the folder, ie. he had a folder of some lolcats, and the folder icon was a a simple yellow folder, open with some of the actual images visibly sticking out of it, another folder which contained documents and images and more folders, was shown open with the actual images, docs and more folders visibly sticking out in the icon.
I really liked that and I was wondering if anyone knows of a plugin or something that can do that on a mac, so can anyone help?

thanks.
- Rob

p.s. I just found a picture example

 

can you please explain what you mean by that and how its done? =)

 

I have candybar and love it, but it can't do anything like what I want or explained. as for leopardMOD, ill look it up. thanks