Here are some of the desktop backgrounds I use on my computers. Pictures are 1024x768 in size and good quality but only displayed in 640x480 for the page. To select as your background most browsers will allow you to "right-click" the picture and you will see an option to use as background. You can also "right-click" and "save picture as" to save the picture to your computer.

I like to use the "blacked-out" versions myself.