Microsoft has been upgrading a Bing theme offered a few weeks ago for Windows 7 customers with new content, automatically.

In the first half of August 2010, the Redmond company delivered the first taste of an auto-updating theme pack for Windows 7.

The Bing Dynamic theme was offered initial with a limited number of wallpapers, but with the promise that additional content would be made available in the future.

Bing Dynamic is the Redmond company’s first RSS-fed theme, which means that the theme pack doesn’t come with all the content it ends up displaying on the users’ Windows 7 desktops, but with just a small subset.

Only a total of four background images were offered to users in the first week of Bing Dynamic’s launch.

However, the subsequent week, the software giant added another four wallpapers. Of course, the theme pack is refreshed automatically, and as long as it is selected as the default theme for Windows 7, users will simply come across new content once in a while, without having to intervene in the least.

“The latest images available via the Bing Dynamic themepack [feature] 4 new images from Cannon Beach in Oregon, Kyrgyzstan, Stonehenge in the UK and some seaweed,” revealed Microsoft’s Rob Margel at the end of August.

Of course, as it promised initially, the Redmond company delivered a new set of wallpapers this week.

“Following on from the 4 from last week we have 2 great new images in the Bing Dynamic Windows 7 theme, this time featuring Zhangjiajie National Forest Park in China and NeverSink Pit in Alabama,” Margel added.

And there’s more to come from Microsoft. Windows 7 customers can download the theme free of charge from the Windows Personalization Gallery and watch it evolve on their desktops.

At the same time, there are additional Windows 7 themes with Bing-related content for users to download and enjoy.

Windows 7 Bing Dynamic Theme is available for download here.

Windows 7 RTM Bing's Best: Japan Theme is available for download here.

Windows 7 Bing's Best 3 Theme is available for download here.

Windows 7 Bing's Best 2 Theme is available for download here.

Windows 7 Bing's Best 1 Theme is available for download here.

The Windows 7 Bing Earth Day student photo contest theme is available for download here.