Is it possible in nautilus that it shows thumbnails only for pictures and for all others like videos, pdfs, etc thumbnails are disabled?
In dconf-tool, navigate to org.gnome.desktop.thumbnailers then in disable key within brackets write mime type of files, it will look like this.
['application/pdf', 'video/x-flv', 'video/mp4', 'video/webm',
'video/3gpp', 'video/x-msvideo', 'video/quicktime', 'video/x-ms-wmv',
'audio/mpeg', 'audio/mp4', 'video/mpeg', 'video/ogg',
'video/x-matroska', 'video/x-ms-wmv']
then delete .thumbnails folder in home folder. DONE
