The gallery scenes are tied to the "persistent" file. If you don't have a backup of that, sadly you'll have to restart the game to collect the gallery scenes.
I have a backup of the persistent file, and I copied it. While most of the gallery has been restored, there are still some missing scenes. It's a bit funny since the later scenes are unlocked, but the ones from the beginning are still missing.
Oh, that's odd. Sorry that its not 100%, but I'm glad most of the stuff has been restored. I think the best method for the earlier stuff is a dummy save and just speed through and grab whatever is missing.
