You don't need to start an entire new playthrough to unlock these scenes you missed! If you have save files from earlier in the game, you can load them up and find these missing scenes in the 'past', and then go to your gallery in the future and they'll be unlocked!
Forest: Whilst wearing the 'undergarments' you can get from rescuing somebody in the forest... proceed as far to the east as you can.
Cave: For that scene, you need to trigger the chest trap, witness the 'scene', and then win the subsequent battle!
Bandit: I think this one is just getting kidnapped by the bandits? Lose a fight to them, do the short little escape sequence and reclaim your gear.
Batcave: When you reach the room with the mineral and get locked in... go talk to the person who trapped you through the bars, and accept their offer.
Misc: I am afraid I can't help if you can't share the hint...