You can download the stock wallpapers of Huawei Mate 9 below. There are total 21 wallpapers, and all are available in high-resolution. It has a huge 5.9 inches IPS display which carry a resolution of 1080 x 1920 pixels, though the company should have supplied with a Quad-HD resolution at such a price range. It is expected that Mate 9 will run on Android 7.0 with EMUI 5.0 UI.
Download them individually by clicking the images to get the full size or just grab the zip containing all full res images.