lmao. I have a single folder with ~3000 papes in it which runs as a random slide show on a minute increment, and then another folder with a few hundred that I didn't want in the shuffle for one reason or another (mostly mobile papes that I like but never use or transfer to my phone as I've used the same background and lockscreen for 5 years). I guess it's "organized" by date (really by name but 98% of them have 4chan filenames so it's functionally date they were posted here rather than download date with some outliers on the ends), I vaguely remember where a lot of them are relative to each other and just scroll through finding relevant papes if I'm dumping in a thread. For threads like this where I only post once I just scroll around until I spot a relevant one, or if I know where one is I'll just go to it's "region" in the folder and usually find it quickly. pic related for example I know pretty well where it is, as it's near the point of the divide between my "modern" collection and the surviving parts of my previous collection were merged together.
I've thought of categorizing them somehow but it really doesn't seem like it would be worth the effort. If I indulge my autism even a little I'd go overboard trying to make a good system of tags, going back and applying it consistently to my existing collection would either be tedious or take a long time done in spurts, and again doesn't bring me much. I may check out the database systems some people posted here, but I think I'll stick to my non-method.