This site has a good mix of HD and widescreen wallpapers. They cover a great number of wallpaper categories and wallpaper resolution in the HD (16:9) and widescreen (16:10) format. For people on Mac OSX, there are plenty of retina resolution wallpapers, as well as the ever so upcoming 4K ultra HD technology. Beyond the different widescreen and HD formats, there are over 4000 downright beautiful wallpapers, handpicked to suit your desktop. Quality obviously outweighs quantity here.