Using the Desktop Background Slideshow Feature in Windows 7

Desktop Slideshow is another cool feature included in Windows 7 which provides capability to switch desktop background images at specified intervals.
Right-click on the Desktop and choose Personalize
Click Desktop Background

Select an item from the Picture location drop-down, or click Browse… to select a folder that contains image files.
Select an option from the Picture position drop-down box. The following options are available:

1. Fill
2. Fit
3. Stretch
4. Tile
5. Center

Set the interval accordingly and click Save changes.
The desktop background will switch automatically after the specified time. Also, if you right-click on the Desktop, you’ll see the option Next Desktop Background Picture in the context menu which can be used in case you want to display the next image.