Since the release of Firefox "5", I've come to really love the new "App Tabs" feature. However, I've now realized that several internal websites at work do not have favicons. So, when I make an App Tab out of these sites, there's only a "blank page" icon in the tab.

Perhaps I wouldn't mind so much if there was only one, but there's at least two or three of these. So, it's just a bit annoying to have to mouse-over the App Tabs to figure out which is what.

I've tried using Favicon Picker 2 to change the bookmark icons, but it only does exactly that - changes the icon in the bookmarks folder. It doesn't change the favicon that's displayed next to the URL in the Address Bar, or the one next to the page title in tabs - the latter being that which is used for the App Tab icon.

So, is there a plugin or other client-side (and preferably "Joe User" friendly) method to assign an icon to a web page or domain, that will be used in the tab bar?