Originally we created a photo-frame using a pi-zeroW with max2play installed (runs Kodi and has an easy web based config interface) but there is a $10 license fee per year so things started to go bad after one year was up.

Current setup is Kodi running on raspbian stretch. Setup instructions for kodi

Once Kodi is running you will need to go to the Settings/Addons and add the Picture Slideshow Screensaver. Then set it up as described below.

Settings/Interface//Screensaver is where you set up the screensaver. Inside that area choose Screensaver mode as Picture Slideshow Screensaver. Choose Settings and set it to turn on after 1 minute, Dim of 100%, effects = crossfade, folder = vmc slideshow folder on the usb drive, length of display=15 seconds.