The Mod Team did something very similar to this a little while ago, we came to the conclusion that you can't separate them into category's unless they're very literal (for example: environment mods, body mods, mixed, game modes.) and doing that would yield too many mods in one category. The conclusion was to just have tags for each mod (so a parkour mod would be, for example: running, environment). Iirc, we never settled on a finished list of "official tags" and the project was dropped when hampa suggested something different.

I don't know about storing nearly 2,000 images where ever you're planing on keeping this "list" when it's finished, but if we can agree on a tag system that works, maybe the Mod Team can try to get it implement into a kind of search on the site, most likely replacing the old "Mods" button at the top (which I think was the original idea).