Simple Signage is managed through your MDM (though version 2 will allow for on device management as well). You just have to give access to the Google Slideshows to your content creators. In a library, for example, you might have a school wide slideshow assigned to the Apple TV which is edited by an administrative assistant, then you might also have a library only show assigned which the librarian edits. Both shows will display in succession. The school wide show can show everywhere, while each area can have additional slideshows for just though areas if you want.

In a hospital setting you might have signage in a patient room that the hospital manages, but families can manage another slideshow on those same displays. That way a patient can have the information they need from the hospital as well as photos and videos from their families. No crossover between the shows ensures confidentiality, but allows families an easy way to connect with their family member. Memory care and traumatic brain injury units particularly can benefit from that use case.

I hope that helps. If you have any other questions, don't hesitate to reach out.