The steam library is a beautiful thing no? So many games at your disposal, all sorts of sorting and flexibility with how you peruse your inventory. Etc, etc. One of my favorite things to do with my games is give them a new preview background. For example, I have this background for Fallout New Vegas. I currently have this for my tf2 background (though I am thinking of changing it soon to better match my love for ). Overall the fact valve even lets you change the background for games is amazing. But I'm far from the most experienced when it comes to Steam's features. As such, I want to ask you...

What's your favorite steam personalization feature?