You'll need to wait a little longer for MacOS Sierra -- July for the public beta, sometime in the fall for the final release -- but you can outfit your Mac right now with a little Sierra flair. The default wallpaper for MacOS Sierra features a majestic, sun-splashed view of the Sierra Nevada mountain range and can be downloaded right now.
To set one of the above images as your wallpaper, open it in your browser, right-click on it and select Save Image As. Next, right-click on the thumbnail of the downloaded image and choose Services > Set Desktop Picture.
(Via OS X Daily)