I have done this once, but I didn't take backup of it...

How do I change the icon in the top-navigation? I want to use a font-awesome icon in replace of the current one. The one that appears to be either gallery.png or gallery2.png, but I can't seem to get it to work. I have looked in the css and around 752 is the area, but maybe something in the latest font-awesome changes could be the reason...Any care to enlighten me?

Brian