HAH! You should see mine.
Admittedly, it's got furry in it, but still.
I've got it broken up into universe (pretty much only 40k, but with numerous faction folders), fetish, number of participants, the Rule 34 directory, etc etc.
Honestly, I do this with everything. As soon as I have more than three pictures of a certain type, I subdivide. It makes things easier to find.