Teach me how to do this pleeeeeaaaaasssseeee!
All I did was replace the background with a gradient I created. There is a Background button in the Themes selection dialog box, if you choose the HyperSimple theme you can click that Background button and select a background image. I used graphics software to create the gradient (I use Gimp, you can use Photoshop, Paint.NET, or whatever) in the same size and format (.bmp) as one of the stock Stars background images (bg.bmp).
I had started to work on a real theme to match the lobby, including the glossy black & red buttons and such, but it was going to be time consuming with all the little graphics fragments required, and with no real documentation I could find other than a brief writeup on the web. Then I found this theme on 2+2 that came close enough to satisfy me until I have the time or inclination to build my own theme from scratch. By then somebody else may have beat me to it anyway.
(Not sure the policy of direct-linking to a "competing" forum, so if you want to download it and read instructions on how to install it, go the Software forum at 2+2 and search for the topic "[Theme]
pokerstars - Dark Gloss (Free)", or PM me for the forum link if you can't find it).