Smashing Magazine posts free desktop wallpapers in every shape and size. The picture you see above is my current background. I love that it comes with a calendar. You also have the option of downloading the wallpaper without the calendar.
I always look forward to the day the new wallpapers will be posted. I'm a little behind this month because my previous wallpaper was a slideshow of Camo, so I wasn't eager to change that.
Head over to Smashing Magazine and find your own fun wallpaper!