The sponsored themes range from luxury car manufacturers like Ferrari and Porsche to beverage companies Pepsi and Coke, as well as Microsoft's own brands Bing and Zune. There are also about 20 nation-specific themes too, which includes most major countries.
While the themes are exclusive to Windows 7 users, anyone can download a wallpaper in the Personalization Gallery. The blog I Started Something notes that it won't be long before other companies offer themes as an opportunity to promote their products and brands.
If you have another location for Windows 7 themes or even a favorite source for wallpapers, share them with us in the comments.