XF 1.2 Custom Forum and Subforum Icons

On my forum, I want to have custom icons for each individual forum and subforum. I've seen examples of how to accomplish this for regular forums, but I'd like to apply it to subforums as well. I have a catch, though; I want to use the same icon for both read and unread. This should cut the css in half, as well, I assume.

I remember on phpBB, I did accomplished this by simply making the an imagepath "blahblah/icons/{forum_id}.png" and then making a folder with all the icons, just with a number as their file. Since I'm very new to xenForo's template and styling system, am I able to do something very simplistic, like that method?