I stumbled on this because Arc-dark / Arc is partially borked on the new Cinnamon 3.2. These work fine.
Once downloaded set the cinnamon 3.0 / 3.2 group folder access to 'access files' and 'apply permissions to enclosed files' in your home folder.
(will require sudo) before pasting into filesystem/usr/share/themes (otherwise they don't show up)
Enjoy.