Apple announced macOS Mojave on the 4th June and introduced Dark Mode. Download the new dark and light Mojave wallpapers here.
Mojave introduces 3 new wallpapers
The Day and Night wallpapers are light and dark representations of the Light and Dark modes.
The third, dynamic wallpaper is a macOS Mojave exclusive wallpaper that will change the background wallpaper based on what theme you set. If you're using anything but Mojave you won't be able to use this wallpaper.
Download the Mojave wallpaper in high resolution below.