I'm not sure about everything else but I LOVE to change the background on my computer all the time. Well, I was searching and I came across this really cool site that posts a set of free "monthly" wallpapers. Each wallpaper is a different design with a calendar on it, if you like that (I do! I do!) or you can download it without the calendar (like if you want a past month's picture).
Here's the site: http://www.smashingmagazine.com/tag/wallpapers/
My favorites for May are the birdhouse one and the sunflower with the lady bug one :)