After a period of inactivity, the Apple TV will automatically begin to display screensaver images. These photos can be customized by the user, and tvOS provides many built-in choices. In addition to the stock images, photos from your personal Photo Stream, iCloud Photo Library, or album artwork can be used as screen savers.
To change the screensaver on Apple TV, navigate to Settings -> General -> Screensaver.
From here, a Type can be selected. Choosing Apple Photos will reveal a list including Animals, Flowers, Nature and Shot On iPhone 6. Shot On iPhone 6 is a collection of iPhone photos curated by Apple and using in the global advertising campaign for the iPhone 6 and iPhone 6 Plus.
Besides choosing a screensaver, Apple TV owners can configure the transition type and amount of time each slide is displayed when screen saver mode is active.