A desktop background image or desktop wallpaper is an important part of your everyday communication with your computer. Some people like it black, some like it white, even gray-scaled, or maybe colourful anime, sexy, cheerful, hilarious or morbid. Choose a background image that best describes yourself and suits your current mood.
Try your luck at Google - type wallpaper and select Large under Size, then click that shiny "Google Search" button, let the search engine do the rest (here's a quick link to easen it up for you). You'll be amazed of the content!
I'd suggest a background with a phrase of some sort, you pick what you like, I have mine (see it here) set today as "Keep Smiling!", found it somewhere on the internet.
Keep as less items on your Desktop as you can in order to make the message readable, you'll soon figure out the reason yourself.