The Chromecast's Ambient Mode kicks on whenever you're not streaming anything for a period of time. Ambient Mode is set to Art Gallery by default, which pulls a curated collection of images.

Your Chromecast can stream content to your TV, but it has other features you may not know about that can be very useful. ... (Chromecast will use the best images you've recently taken).

The original 4K, $49.99 version of the Chromecast with Google TV was announced in 2020, and now when you go to check out in the Google Store, there's a "screen resolution" option for "4K" (still ...