I agree, I really don't know what the point of the photos app is if it doesn't show me my photos. It only seems to show shared folders. How is that useful? I bought the 64gb Apple TV expecting to be able to store a lot of photos to flick through and for a screensaver but now I see no photos. I don't really use shared folders (and I don't know anyone that does, though i'm sure some people do) so why limit it to just these photos? Hopefully they fix this soon.
This is not hard to understand. The TV may be tied to one iCloud account out of necessity, but it is a shared device. It is preferable that this device only show Photos that are deliberately shared. It is welcome that it has that level of security, so that not every single photo you snap ends up on the TV.
Photos that you Share are very likely akin to photos that you "wouldn't mind seeing pop up on the TV" for anyone that happens to browse your photos or watch your screen saver, etc.