I have noticed that Thunar (0.8.0) doesn't seem to thumbnail most JPG-files. It seems that it refuses to do this on bigger JPG's (400-500 Kb), but not on files belwo 250 Kb (note I am unsure this is always true; it seems to fit the pattern I am seeing). Right-clicking a file, then changing 'Open with' without making any change to the sofware specified there does create a thumbnail. Browsing that folder with nautilus first, and then going back with Thunar solves, presumably because either action invokes the gnome-thumbnailer.
I have been trying to understand whether Thunar has a size-limit above which it doesn't do thumbnailing, but cannot find that in the docs. I have found a comment that suggests Thunar will only JPGs provided these contain a thumbnail in their EXIF data.
Anybody who can provide guidance how to resolve this?
BTW: I note that I have significant numbers of files in ~/.thumbnail/fail. Deleting ~/.thumbnails and then browsing to one folder shows that the number of files in ~/.thumbnail/fail matches the number of JPG's for which I see no thumbnail, so somehow my JPGs are not up to standard>