If you want custom themes beyond what Google provides, I'm hawking a tool a hacked together a couple of weekends ago. It's a just-for-fun thing so the UI is pretty sparse, but it works! :)

http://sexychrome.com

I'm a big fan of Chrome. Favorite features include the speed, full-screen browsing, detachable tabs. Needs a robust extension for CSS inspection/manipulation, though. Built in one doesn't quite flow as well as Firebug. Decent JS console.