Sometimes, Gnome doesn’t show the thumbnails, whether for videos or pictures. It can be by the lack of a thumbnailer, but almost because the location of the thumbnails folder has changed !
Now, the thumbnails are stored under the .cache folder.
To solve the problem, just follow these steps:
- Go to your cache folder : cd .cache
- Create a symbolic link to the folder (.)thumbnails in your home folder: ln -s ../.thumbnails thumbnails
- You now get a link in .cache to thumbnails:thumbnails -> ../.thumbnails/
Open Nautilus and see the previews appear !