Wallpaper images are free and are yours for the taking. You will find 1024x768 and 800x600, select which ever you'd like. Please note that these images are high quality BMP formated images, therefore they may take time for the page to load, as well downloading.
To set an image as your wallpaper (first, click on the thumbnail image from below to load the full sized image webpage)...then simply right click on the image and choose the option to set as wallpaper. (Mac users click and hold, since they only have one button). Or you can right click and choose "Save Picture As" and save image to your c:\windows\ folder or your default wallpaper folder.