The "Random Image" tile displays a random image selected from the Sharepoint Picture Library specified in the "URL" setting.
The image can optionally be linked when adding a column named "URL" to the picture library.

Example: This example displays a randomly selected image from the"Pictures" Sharepoint picture library. Also, the "/daily" parameter is added to the "Content" setting to display an new picture every day (as opposed to a new picture on each page request). The tile also displays the image "Title" (if present). Content:/dailyURL:http://somedomain/Pictures/Forms/AllItems.aspx