Eg. http://cs2d.gamebanana.com/skins
The CS2D section recently got updated there and every skin was classified into sub cats.
There are cats for each CS2D weapon in-game as also cats for misc sprites if a sizeable amount of weapons exist to justify the making of such a cat.
Benefits?
Easier to browse skins. Eg. I want a Desert Eagle skin for my game. I can just click on the Deagle section.
A search filter using the keywords "Desert Eagle" or "Deagle" isn't actually that helpful since skins for Desert Eagle can also be a Colt Python, an M1911, etc. Instead of searching all these terms and checking whether that skin is meant for Deagle or other pistol, I can just browse the Deagle cat instead.
Drawbacks?
Mods will need to do heavy work during classifications.
DC may have to do some website modifications.
Classification can be a community effort with Mods asking people to make lists. Like a guy can browse the current section from pages 1-10, classify all skins. Some can do 10-20... and so on.
Website modifications on the other hand might be complex and DC alone will have to handle that