the gallery is for image unlocked in event, scene are replayable by interacting with the character the same way that the scene was unlocked, so no gallery for animation, only event image.

There is an in-game photo album once you find the camera item.  Won't spoil anything else so just search around carefully and you'll find it

I think that the replay gallery will be implemented towards the end of development, so if I had to guess, I'd say expect it in the last 2 or 3 updates before the full release. If memory serves, it was like that in the first game (might be completely wrong here, so don't take my word as law)