Every new release of Android comes with some new wallpapers and Android M is no different in this regard. While the OS is still in developer preview, it comes with a new stock wallpaper, and new system and notifications sounds.
While there is only one wallpaper in Android M currently, it is likely that Google will add a few of them when it releases the final version of the OS sometime in Q3.
If you are looking for the Android M wallpapers, system and notifications sounds for your device, grab them from below.
Click on the wallpaper, then on the page that opens, right-click and select the ‘Save Image as’ option. Alternatively, you can download the wallpaper directly from here.
The stock ringtones, notification and system sounds can be downloaded from here (.ogg format).