Are there any scenes NOT in the Gallery?
Yes, there's a lot of them. Currently, in the gallery you can't see:
- Any of the rescued witches. They also don't appear on the same savefile you have rescued them before. Once gone, they are gone for good. BonedMod, talked about above, partially solves that by respawning rescued women, but comes with it's own caveat of gameplay changes. A scene with two rescued witches from underground church does appears in the background of the gallery, but it's a rare exclusion, because they initially were part of gallery background and were added in the world later;
- Overwhelming majority of background scenes. You can still find them in the world, since, unlike rescues, they don't despawn, but not in the gallery. Gallery does have a unique girl inside tentacle maiden on the background alongside two rescueable witches, but I'm not sure if they should count;
- Any of the events. Most of them are similar to background as in they don't deactivate and you can replay them over and over, exclusion being teleport to the Ranch, because it basically acts as Suzune's rescue;
- The high karma game over options, that is listed as ??? when you don't have enough karma. It's a single still image tho, so not much lost there;
- Diaries and logs. They have a few still pictures for each one, but can't be viewed from gallery. You can still view them in the game on shelter's second floor and in the Ranch;
- Any of the girls, who end up at the Ranch. But you can, obviously, find them at the Ranch whenever, they aren't, fortunately or not, actually being sold off anywhere. Honestly, Ranch acts as a bootleg gallery, wish there was a way to make it's unique enemies non-hostile somehow;
- Few miscellaneous scenes, including: part of Prayer Maiden game over; unrescueable witch in pleasure trainer on White Cathedral Rooftops; high inquisitors stoprape on the same level; perhaps some other I can't remember.
And that's the extent of it. For now. D-Lis mentioned in last update, that he's working on adding them to the gallery. Looks like long-forgotten "Player" option in Punishment Room might be used to view background scenes, as well as some other.