Pretend I don't know what that means
So what do I do. Do I go into the, in my case, GemItems.java file and add getIcon? Or do I add:
itemIcon = iconRegister.registerIcon("unlocalized name") ?
Or do I do something COMPLETELY different?
Register all of the icons in registerIcons(IconRegister), instead of just one. Then redefine getIconFromDamage(meta) in the same class, just like you overrode registerIcons, and tell it to return the appropriate icon (you'll have to make a list, or else three variables) for the given metadata.