I found Gloobus-preview and thought it's kinda cool. Is there any way to get this to work in Files? Tried using the configurator and change the previewer path to use Gloobus but it's not working on Freya.
I was also trying to figure this out. I found the following article (& comment) describing using dconf-editor (the configurator you mentioned?) to set gloobus-previewer as the previewer http://elementarytips.blogspot.nl/2013/04/gloobus-preview-in-elementary.html
Later on I found the following bug report, which sadly finished in a won't fix. https://bugs.launchpad.net/pantheon-files/+bug/1400501