I'm sure this has been done elsewhere, but I can't find other example images. Due to the way the frosted glass obscures what's behind the dock AND the way the screen zooms (if you haven't turned that off) when you select a folder to show its contents, you can use the combination of the two for an interesting effect.
Set this image as home screen, and open a folder of icons for the reveal You could type a message there that would only be seen when viewing a folder's contents, too. There's not a lot of space to play with, but there are a lot of fun possibilities. I'll be updating my Keynote template with the dimensions for anyone that wants to play with OR export to PDF and open in the illustration program of their choice.