As you may have noticed Windows 7 Starter doesn't allows you to change the desktop background, there's no default option for this purpose and it's quite annoying!
But did you know that there are some software allows you to perform it:
- Download the program and install it
- Once done simply right click on a particular image, a new option has been added to the context menu "To choose like wallpaper"
- Download and install on of the free themes
- Launch the MyColors program
- Click on the Wallpaper tab and wait for the program to populate the thumbnails of the image present on your PC.
- Select the one you want to use.