Just found this amazing app called Equinox which allows you to create your own dynamic wallpapers for macOS. It is open source and you can download it on the Mac App Store.
Opening the app will prompt you to select one of three types of dynamic wallpapers:
Appearance-based wallpapers use the current dark/light mode state to determine the look of the wallpaper. To create one you just have to drop in two images and specify which one should be shown in light or dark mode.
Equinox even features a solar calculator to create wallpapers that match the position of the sun at your exact location. Here you will need a few more images but the results are stunning. You might want to check out this gallery of dynamic wallpapers to get an idea of what they will look like.