I was disappointed with Debian's choice for Iceweasel icon, so I made a script to replace it (all the many instances of it in the package). You can find it at: www.alphapapa.net/debian/iceweasel It takes a local file path or a URL as its argument. Run it with sudo so it can replace the files from the Debian package. I put my favorite icons in that directory also, and there are even more at https://wiki.ubuntu.com/IceWeaselIcon