I don't get any image previews in Pantheon Files.
I already did the chown of the .thumbnails folder as suggested in various other places, but that didn't help. The thing is: I do get previews for PDFs and Fonts. I also tried the following: I put the tumbler.rc from /etc/xdg/tumber into ~/.config/tumbler and set PDF disabled to true, with the effect that there were in fact no PDF thumbnails generated anymore. So somehow tumbler does work, and even reads the tumbler.rc correctly and can write to the .thumbnails folder. Just not for image previews (not JPG nor PNG etc.).
I am by far no linux expert, so I am pretty much stuck now how to proceed.
Btw, on my laptop everything works fine, just not on my workstation. I did update, upgrade, dist-upgrade etc. on both of them.
Edit: Just saw that I also get previews for BMPs.