Apple is currently in the process of updating its dev site with a new Lion build. Once it goes live, I'm sure the wallpaper will appear on the Internet soon (I'll post it in this thread later tonight).
The concept behind the fabric is that it is behind the OS. It's what you get when you remove all the GUI. Hence it's there behind mission control. It's there on the unused screen when you full screen dual screens. It's what you see behind web pages when you scroll. It's there when you shut down and also now when you log in.
So really it's meant to signify the "behind the scenes".