During the release of Windows 8, Microsoft also updated their Personalization Gallery and now has it merged with windows.com all together. From there, you now can download tons of themes and background images to make your Windows 8 more personalized with beauty.
The themes page contains a lot of nicely done themes from all sorts of categories. Each theme has its own detail page that reveals more details about the them as well as what versions of Windows are compatible. Basically, all themes are compatible with Windows 8 and Windows RT. Thanks to the backward compatibility. But not the other way around.
Simply click the Download link on the thumbnail listing page or Download Theme button from the detail page to download the themepack. The download the themepacks with .themepack as the extension name work on both Windows 7 and Windows 8. The ones with .deskthemepack only work with Windows 8 and Windows RT.
To start using the theme, double click the themepack file you just downloaded. All desktop images, color settings, and sounds will be automatically imported to Personalization window. And the theme will be automatically switched to the new imported theme the same time.