From the 'pimping your browser' files:

Google is out with a new Themes Gallery site for Chrome users - but not all Chrome users.

The new Themes Gallery currently is only for dev and beta channel users running Chrome 3.x.  So for stable Windows users, you're out of luck.

For Linux and Mac users, there is no stable version, only the dev version, so you are in luck.

Currently there are 49 themes in the gallery, which enable a Chrome user to change the look of their browser. This isn't revolutionary technology, but it is a feature that a modern browser should have, and now Chrome has it.

In comparison, Mozilla now has 20,000 different Personas (basically themes) available for Firefox users - so yeah Mozilla has a bit of a lead there. But hey you gotta start somewhere.