Most of the PC users including me preferred to use a dark wallpaper for their desktops. It could be the reason that all the app icons appear to be more outstanding against the black-themed background.
Here you go a collection of beautiful dark wallpapers that I’ve put together. Download them and give it a try on your desktop, or you can easily crop the wallpaper for your mobile devices too. Most of the smart phones have default image cropping feature.