Alternatively, implement a tag system. Adding tags is simpler than manual sorting and making folders for each exact situation. The more girls you add and the more tags you support the better the system gets.
(The more tags you filter by the less available girls. )
While this can be better organisation wise, it doesn't change the fact you would still need a huge amount of pictures to keep it balanced content wise if you want it to stay as similar as possible between all rooms the raider go through.
Personally, as long as it keeps the same class and body type, i'm good. Hair color changes can be noticed sure, but it's a fair trade if it stays the same type of girl while she's getting goo'ed or web'ed.
The consistency of pictures for raiders is a "problem" here since the beginning, and while i find it understandable to be bothered a bit by it, people should remember that the game is at its beginning and isn't just a picture shuffling app. And also, not every type of character have met all the monsters/status that are or will be in the game. For example, maybe there aren't any light purple haired knight being defeated by a demonic spider out there on the internet (or easily accessible). So you'll probably get a green haired one instead for that battle in your dungeon. Will that really bother you even tho you still get to see a knight get captured and boned by your monster ?
I understand people wanting more and more consistency, but you gotta understand that it requires either time to find more pictures (and make sure they're corresponding with others for consistency) or to hire artists to make them, and right now, more content isn't needed for the monsters/traps already available. i would rather see rank 2 unlocked and new traps/monsters for a new variety of content, rather than just more and more slimed girls but "more consistent" during the raid. Won't lie, when i get a 8+ raiders night, i don't give a damn about consistency, i won't even remember what classes were the first 6 raiders until i reach the end of raid night screen.
Sorry about the rent ya all, and especially dusty stu since i did it while answering your post

, but i needed to get that out.