This is kind of a subjective part of your computer because there are a number of different things that you could use your Desktop for. Maybe you have a special background image set up, maybe you have hundreds of files and shortcut icons, maybe you have nothing and you barely use it. I would like to share my personal use of the Desktop with you and my reasoning behind it.
For me, the Desktop is a place of temporary storage for files only. I never have a program shortcut on my Desktop and I never have a file there for longer than a week (after that it gets filed away into a more permanent location). This allows me to keep my Desktop free of clutter and still access all of my needed resources quickly and easily (through the use of other tools and tricks). I also have a plain black background that helps make file names easier to see because of the color contrast.