Comment 7 for bug 986032

Thanks pacho, that's a helpful link.
If you download the tarball for the revision before:
http://bazaar.launchpad.net/~ubuntu-art-pkg/light-themes/trunk/revision/223?start_revid=223
Then you can copy the missing files back into your /usr/share/themes/Ambiance/gtk-2.0 directory and there we go, MATE looking nice on the latest Ubuntu :) Just for the benefit of anyone googling like crazy like I was.