Windows 7 has lot of changes in the UI when compared to Vista and one of the changes is the way wallpapers are controlled. In Windows 7 you can change wallpapers automatically from a collection after a specified time. If you have selected more than one wallpapers in Windows 7, then you can change desktop wallpaper quickly from the right click menu in Windows 7. For this features, you first need to make sure that either your theme has multiple wallpapers or you have selected multiple wallpapers from a folder.
To do this, right click on the desktop and select “Personalize”. Navigate to desktop backgrounds and select multiple wallpapers, you can also browse for any folder where you have wallpapers.
Once you have selected the wallpapers in desktop background settings, then you can change wallpapers by right click on the desktop. When you have multiple desktop backgrounds set, the right click menu shows an additional option “Next Desktop Background Picture”.
When you click on this option, the next wallpaper in the list will be set the background picture for your desktop. This way you can quickly go thought the set of wallpapers enabled. This option is automatically enabled if you theme has multiple wallpapers.