Apple announced its new OS X on Monday, dubbed OS X Mavericks, but unless you've got a developer pass and fancy dabbling with beta software for the next five months or so we wouldn't recommend you download it
One alternatively though, is to give yourself the feeling of having it already by downloading the new Mavericks hero wallpaper.
Apple has made the Mavericks wave wallpaper available for all screen resolutions with a source file that measures 5,120 x 2880 pixels in dimension. That's plenty big enough for your Retina MacBook Pro or your iPad.
Of course you don't get any of the new features - you're still using Mountain Lion - but you do get to see the big wave every time you open your laptop.
You can get the new Mavericks wallpaper here.