MacOS 10.12 is out in beta. Early beta tests can be buggy though. If you want that fresh Mac feel on your current version without the risk—or on your PC for that matter—you can download the new wallpaper.
As Mac OS 10.12 is code-named “Sierra”, it’s only fitting that the background would feature the lovely Sierra Madre Mountains, in all their sunset-drenched glory. It comes in high-resolution at 5120×3684 pixels, which should be large enough for pretty much any monitor out there.
You even have two versions to choose from. If you want to see more of the sky as you gaze at your desktop, presumably pondering the deep questions of life, grab the version from Apple.com. If the stone and shadow of the mountain is more to your fancy, grab the version from 9to5mac.com.
Also available from 9to5mac is the largest available version of the iOS 10 wallpaper. It’s available in iPad and iPhone-centric resolutions, so you can lose yourself in green sea foam on any mobile device of your choice.