Sharing photos with AirPlay via the Share action is pretty cumbersome right now and not very intuitive. Also when you choose to mirror the screen, others can see thumbnails of all your photos or see photos you don’t want to show.
This app allow easy presentation of photos on Apple TV with only explicitly selected photos. I am not sure about the available options but there should be a way to change how app looks on mirrored screen.
Another possibility would be to leverage the MultipeerConnectivity framework and have host tvOS app and guest iOS apps that could be sending pictures directly to it. This way multiple people could present photos.