Set your desktop background to a single photo or to a slideshow of photos.Set a desktop background or slideshow
To set a single photo as your desktop background, select the photo and choose FileSet as Desktop Background.
You can also set your background to a slideshow of photos. To do this, select the photos for
the slideshow and choose FileSet as Desktop Slideshow....
Shotwell will prompt you for a slideshow delay, which can be any interval up to one day in length.
The background slideshow will proceed even when Shotwell is not running.