You can set up screen savers to display whenever Apple TV is idle. Some screen saver options can be personalised to include memories and slideshows or portraits from your photo library.
Go to Settings on Apple TV.
Go to Screen Saver > Memories & Slideshows, then on Apple TV.
Go to Screen Saver > Aerials, then choose whether to show or hide Cityscape, Earth, Underwater and Landscape themes.
Select Download Frequency to choose how often you want to download new Aerials.