I wanted to change the default icon for one certain file-type on Ubuntu GNU/Linux, because the icon for this file-type would otherwise have the blank paper icon. In this example will use: .torrent files
- I have downloaded a .png file of the new icon that I want to use.
- Rename that file to: "gnome-mime-application-x-bittorrent.png" (for other file-types change 'x-bittorrent' to the proper name of your application)
- Move that file "gnome-mime-application-x-bittorrent.png" to the folder ".icons" in your home folder. In case the ".icons" folder does not exist simply create it there (mkdir ~/.icons)
Based on the following thread from UbuntuForums: http://ubuntuforums.org/showthread.php?t=355714