Here's how my sorting system works - it's similar to what I do on my hard drive.  I use digkam now, but used to do this

with symbolic links.

Imagefap doesn't have folders containing folders, but I do something close enough with the folder names. 

Instead of using '/' to separate I use '.

The folders are actually tags so the same image can be in more than one favorite folder.

celebrities.*

-- Contains any real people whose name I know including pornstars, politicians, news anchors, vloggers, pop idols, etc.  If I discover a new nude model and I'm fan enough to learn their name, they go here.  

characters.*

-- Contains characters from shows whose name I know.  This includes canon characters and eg: cosplay of them.   Grey area includes 'Princess Leia'.  Jabba the Hutt might have used the famous slave getup more than once.  Is a cosplayer trying to dress as Princess Leia specifically, or just one of Jabba's slaves?  But toons of Princess Leia definitely qualify.

Monstrosities.*

-- Contains monsters.  Naughty Tentacles, even Ugly People.  For instance Bowser is a Monstrosity, but so might Zapp Brannigan be considered a 'Monstrosity' to Turanga Leela because although they had a tryst in the show, she eventually found him creepy and annoying and he just kept coming. 

shows.* 

-- Contains characters I personally don't care enough about to put in characters.* so I am going to condense all the characters from that show into shows.* 

jobs.*

-- Contains people doing jobs

Maledom.*

-- A male appears to be dominating

Femdom.* 

-- A female appears to be dominating

From here on I need to explain capitalization.   Since image fap doesn't allow both folder-name and Folder-Name,  one of them will get a trailing underscore_ to disambiguate.  For upper level folders (eg characters, and 'Maledom') and proper names the capitalisation basically meaningless.  Lowercase is easier to type and is the default, but Uppercase can be used for aesthetics, it's really meaningless for upper level folder names, but I suppose it might reflect the case for most of the folders inside.

However the lowest level of the folder name, eg: jobs.nobility vs jobs.Nobility_ the case has meaning referencing whose perspective I find most interesting to identify with in the pic and who is dominating.

Consider a drawing where Bowser is raping Princess Peach in the ass.

I don't necessarily self insert at all in a pic like this.  I am not a Turtle Dragon and I am not a Princess.

It belongs in characters.Princess-Peach and Monstrosities.Bowser. (duh)

It belongs in Maledom.ass because it is Peach's ass that is being raped.

It belongs in jobs.nobility because Peach is a Princess currently being taken down a peg.

If Bowser were a King ( is Bowser a king? If not he's at least a Warlord which counts as Nobility as do the Wealthy and Famous ) it also belongs in jobs.Nobility_ because Peach will be worshipping the King Turtle Dragon's cock with her sweet mouth as soon as he pulls it from her ass.

It also belongs in Maledom.spoils-of-war because Bowser kidnapped Peach and she's now a spoil of war to do with as he pleases.   He 'earned' her by risking life and limb for his prize.

But Maledom.Spoils-of-War doesn't make sense because that would mean someone captured a male warspoil who is somehow dominating them while being their prisoner and the perspective of the victorious capturer who is being dominated by their prisoner is the salient and interesting thing about the pic.

It belongs in Femdom.Not-For-You.Trophy-Wives if Peach likes Bowser now and you coudn't get a girl like her  (prevented by too many cock blocking Goombas), especially if she looks like she knows it and could be about to let you know that fact or remind you of it, or tease you about it.

If the pic were Peach and Mario, then it would belong in Maledom.wives.trophy because Peach is canonically a literal prize/trophy.  But I am using the word 'trophy' to mean something possessed and displayed.  It's not such a big fetish for me as the amount of porn that fits into it might suggest, but since porn is about displaying skin, the catgory gets spammed.

So to recap: jobs.teachers would be for a student  (maybe it's you) blackmailing a teacher, but jobs.Teachers_ would be for a teacher demanding oral from their student (maybe it's you) for a deperately needed grade.

A word about Milves, Gilves and incest...

I've never been into incest in real life.  Not even a little bit.  Not even fantasies.  I've tried, experimentaly, fantasizing about blood relatives, but my dick won't have any of it.   It's not even a temptation, and I'm old enough that I am sure this will never change.

Milves however are another story.  Yes please!  And though I'm now older than most 'milves' if I bother to label them as such, I'm likely as not imaginging myself as much younger than them.  The category gets spammed though because there are lots of good pics that don't imply that.  If the folder gets too big I may have to split for instance milfs into out into Maledom.moms ( structured like Maledom.wives with good bad trophy stepford etc ) leaving generic milfs.  But then one of the categories might be neglected and the list of categories gets longer.  It's a compromise. 

I've never had a 'step' anything and don't have any 'adoptive' anything, and wouldn't cuck my own Dad because he's not an asshole, but if he WERE an asshole, and I had a Stepmom, and somehow we ended up fucking, I would call her MOM and never mention 'Step'.  Same goes for any other relation. 

If doing something delicious and better than not doing it in every way it's ok.  It may not be ok for a society to allow it, but in "God's Eyes" ( I'm atheist ) it's fine.   There may be certain people and cases and relationships where even blood related incest is ok.  I mean I've never had a sister, but maybe getting a blowjob from your sister could be good if you could handle the mess.  As long as you don't knock her up it's all about the emotions. 

Like 'Trophy Wives' incest is a sink for porn and blown way out of proportion by the amount of porn that fits the category.

But Incest is a great trope for fiction and fantasy because it has the Romeo and Juliet factor.  If the Montagues and Capulets weren't feuding, Romeo and Juliet have just gotten married and fucked like bunnies and had lots of children, living happily ever after but that would have been a boring story.   

So I have made peace with incest in porn.  I'm not going to awkwardly delineate 'step' or 'adoptive' or role-play etc.  If you're role playing or fantasizing, you certainly don't call attention to it.

Nuff said.