That is probably based on the screensaver used. I know I don't have the same screensaver on all of my Roku devices, but I don't use one that uses a photo stream. It's possible that specific screensaver links itself to every device on your account.
Dan
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee, just another user.