there's a weird bug in Windows that prevents thumbnails for being auto-generated for certain video filetypes (mkv, mostly, though the codec used might also matter, not sure). the workaround is to put an image in that directory and open it in Microsoft Photos, then pull open the little filmstrip file picker at the bottom--any video files appearing on that strip will get a thumbnail right then and there.
so I keep an image in my OBS output folder so I can occasionally generate thumbs for the videos I've been recording, mostly to make it slightly easier to tell what's what since they're all just named by date until I have time to go in and rename them to something more sane.
anyway, this is the image I keep in that folder. it is named zzz_kennyrogers.png.
