Topic icons in the recent topics block

So everything is working fine, and I have the block on the side which displays the recent topics posted. Each topic has the little icon next to it that says if the thread it unread or not. I'd like to change that a little though. What I'm wanting to do, is make it so it displays the topic icon of the thread posted, either next to the unread icon, or in place of it. Seems easy enough to do, I just have no idea where I'd go to edit something like this.