Ninja was made by Don5318 for Wincustomize Windowblinds on MS Windows. For you dual Booters out there, be sure to check out his work.
Don kindly granted permission to port this to Linux. I previously made a port to XFCE but making a port to Metacity/Mate/Cinnamon was a bit trickier because Metacity does not permit an image to extend beyond its borders as XFWM4 does.
This is in two versions: with CSD and Without CSD.
IF you peruse my other uploads, you can read all about gtk3-nocsd, (how awesome it is) and how to install it.
Extract contents into /usr/share/themes