When the Win7 beta was released Microsoft had a witty default background greet new users. The background consisting of a Betta (get it? beta, Betta?) fish and 7 bubbles was a well-done, light and colorful. Now that the Win7 RC is in the hands of the masses the Betta background doesn't seem to fit.
So in the vein of the original background I've put together the official, unofficial Win7 RC background; enjoy.