A great application to manager theme in Ubuntu is the GStyle. With it you can download and install full themes, Gtk themes, icons themes between others from gnome-look.org. Also GStyle permit to set a theme for cube mode. To install it, open a terminal and run:
sudo add-apt-repository ppa:s-lagui/ppa
sudo apt-get update
sudo apt-get install gstyle
To run it, press super key and search by GStyle. Follow below some GStyle screenshot.
That’s it. See you next time.