My favorite feature of Windows 7 is the Desktop slideshow. There used to be applications which you had to download separately to do it, but I like it. I don't have many myself, but it's always fun using my friend's computer as he has about a hundred funny or meme-based wallpapers which changes quite often. If you don't know how to do this, right click on your Desktop and choose Personalize, then Desktop Background. Hold Ctrl while you select wallpapers. You can choose how often they change and you can choose if they shuffle the order.