Im using Ubuntu 11.04. In Elementary nautilus, I can preview a music thumbnail by hover the mouse cursor on it. But I cant do it with the video files. I've set "Only for the files smaller than : 100MB" in Preferences/Preview but nothing changed. Please help!
If you're using nautilus elementary, you can try gloobus.
Previewing video like that is not possible on nautilus - at least not yet.
By the way, for the part with the music thumbnail : it is possible on both standard nautilus and elementary one, not just on nautilus elementary