Hey MasterFruit!
There are a few scenes that can be missed on a playthrough.
"Useless Mutt" is when you first start dipping into Lyriel's dreams where she's dreaming of being a slave.
"Alchemical Mishap" is related to an event in game that also unlocks for Cait.
"Pre-reveal Service" is when its just you and Rae in the house, when you visit her in the attic again.
"Punk-Gal" is at the very start of the game when you're chilling in the park.
"Special Order" is from the space dream and can be done at anytime.
And "MILFing It Up" is when you dream of the pool in the backyard for the first time and have a choice between Jenny and Vivian.
If you have missed these, I suggest to make a dummy save and just speed/skip through the game to those points if you wanna unlock them for your gallery. I know its not ideal but I hope these help pinpoint where to snag em!