Light Void (Free Version) is a simple, clean, minimal and flat icon pack with matching wallpapers, and matching clock widget. Icon centers are transparent creating a window to the background behind them. The hollow icon center changes with whatever is behind it making the entire display blend together very well. Over 200 hand-picked wallpapers of skies, landscapes, and abstract designs are included.
You may need a 3rd party launcher to apply the icon pack. If your stock launcher doesn't support icon packs, you can use apps like Awesome Icons or Unicon to change your icons without using a 3rd party launcher. You can manually edit icons in most launchers by long-pressing the icon you'd like to edit.
This is the free version of the app. Get the pro version here: