In the current incarnation of the Apple tv there are some simple photo based screensavers to choose from. In the new tv os, is it possible for a developer to create screensavers available to Apple tv users?
tv os screensaver
Unfortunately what you're looking for is not available in tvOS 2.0. Please file a radar at http://bugreport.apple.com as a suggestion for a future release.
I came across one of the best 4K UHD screensavers in youtube. Please check this: https://youtu.be/Bmd6-WA2Ok0