The final update for May 2011 has posted for the original Bing Dynamic RSS Windows 7 Theme and includes two more shots that bring the theme up to a total of 50.

Underwater Wave

Underwater view of wave in Hawaii

Bryce Canyon Amphitheater

Amphitheater, Bryce Canyon National Park, Utah

There have been some great additions recently and the variety of shots are tremendous.  We should see updates for the new Bing Aerial Imagery RSS Dynamic Theme in the next couple of days as well.