Apple TV Photo Slideshow Repeats Photos Over and Over

The slide show option should run though all the photos in an album, either from the Photos app or from Home Sharing’s Computers app. Not sure what the limits are (undocumented for public support articles), if any. In both cases, the set can repeat if so configured in the options before the start of playback (Repeat: On|Off).

The screen saver option will create a slide show from loading a limited subset of album images, as these are copied to the Apple TV box’s cache. This will be limited by number or images or total of the file sizes, and/or available disk space (undocumented). The set will repeat after all have been shown, as screen savers only end by other actions (interrupt actions or sleep mode).

I think if you're running the slideshow for a certain album, the slide duration must be long enough for the next picture to load (e.g. 5 or 10 seconds). If there is not enough time, Apple TV will back track to an earlier slide and go forward again when the batch of newer slides finish loading. I use Verizon FIOS and the 2sec duration always causes repeats, 5 sec has a lot less repeats for 4k photos.