Into the game itself? I actually thought about it, but the full resolution images are 15mb per illustration and there's 17 of them, so I opted not to, at least for this game. I do think next time I'll consider the idea of a gallery much more.
Not so well versed in RenPy or Tyrano coding but couldn't it perhaps be possible by making a gallery which jumps to X/Y/Z event module thus making a gallery with minimal size increase?
I suppose so, additionally I don't know the difficulty of this suggestion, but perhaps it could be possible to add a keybind to the Hide text function, that way it might be more convenient to serve as both a replay system and a gallery.