MessageCounter which is in development as well. So without any wait, here are 2 images. Click on them for a full screen version and download to use them as you like.
The following images are licensed under Creative Commons license. http://creativecommons.org/licenses/by-sa/3.0/. You are free to use these images subject to the terms of this license.
Material design Wallpapers by midhunhk is licensed under a Creative Commons Attribution 4.0 International License.
Update: One more artwork is here. This one is my current wallpaper.
Update 2: The complete wallpapers and as well as future updates can be found at : https://plus.google.com/photos/114665288998361746888/albums/6121148941176472961