I’ve just upgraded my Mac to the latest Mojave beta, and I’ve discovered a new wallpaper!
In a previous update the Desktop Pictures folder was split into two sections – Dynamic Desktop and Desktop Pictures. The first section containing the photo of the Mojave desert, which contained a dynamic, and two still (night and day) versions.
This new one is called “Solar gradients” and comes in just a dynamic format. Of course it’s a rather simple wallpaper, and the majority of the time it’s a two-colour gradient, but it will show you the sun rising, the sky getting brighter, followed by the sun fading away, and a darker blue and black combination for the night sky.
A quick tip – If you want to preview a dynamic desktop, when you navigate to the Desktop & Screen Saver pane in System Preferences, just select the wallpaper, and the preview image will cycle through the different segments.