Microsoft has again come up with some more Windows 7 themes -
Transformers 3 theme -
You can download Transformers3 themepack from here.
Castles of Europe theme -
From medieval ruins to Gothic Revival castles, this free theme for Windows 7 brings to your desktop some of Europe’s most beautiful châteaus, fortresses, and castillos. Includes architecture from Scandinavia, France, Spain, and the UK.
Download the Castles of Europe theme from here.
Paramount Pictures Movies dynamic theme -
Automatically receive new wallpapers from the latest Paramount Pictures movies, including Thor, True Grit, Kung Fu Panda 2, Super 8, and Transformers 3. This free Windows 7 theme updates automatically through an RSS feed. (More info on dynamic themes.)
Download this dynamic theme from here.
For more themes released earlier, please check http://windows.microsoft.com/en-us/windows/downloads/personalize/themes