Looks like a couple of small stand-offs - there are at least two mounting holes in the Pi board.

Amazing design , I really like this. How is the pi suspended ? Are there any more pictures ? 

Awesome. Can you give us some details on the build?

Oh man I just tossed out a bunch of those plates!

Here's the secret sauce: http://imgur.com/Ob4VZdi a mounting clip that is bolted to a short standoff in the middle of the bottom plate. 

Some standoffs and two cover plates from dead hard drives plus rubber feet. http://imgur.com/DVsD4Su

Pi case from old hard drive parts