Gnome could use of an instant preview feature. This is different from thumbnailing.
Gloobus is an extension of Gnome designed to enable a full screen preview of any kind of file.
-it's not about tiny or medium sized miniatures of your files -currently there's no miniature for half of the file formats you're using (and besides we want a full screen preview). -we don't want to load the application -the idea is to hit the spacebar and get an instant preview of the file
Designed as an extendable, standards-compliant previewer , so that it plays nice with Gnome and can be easily extended to support any kind of file, Gloobus enables instant previewing of your files, without even having to open them. Hit space, and BANG, here's the content of your file, displayed as it would if it was opened.
Currently, Gloobus supports MP3, TXT , PDF, JPG, PNG. It has a sleek black interface which will put your files in focus
[http://ubuntuforums.org/showthread.php?t=828774 Ubuntuforums Thread]
[http://www.getdeb.net/app/Gloobus Deb Package for Ubuntu]