A wallpaper site can be good money making site. All you need is a good collection of wallpaers and a good wallpaper script.
For wallpapers, just search on some webmaster forums. You can get thousand of high quality non-watermark wallpapers for as low as 5$.
Now, you need a wallpaper site script. This can be free. Below [...]

You must care to use image of light size. Heavy images on your site can make your web site slow. One way to decrease size of images is by compressing images. Any good image editing tool can be used for compression. A good image tool should be used to make images, buttons, header image, navigations [...]