Theme E17Gtk created specifically for the desktop environment E17. Is a dark theme with rounded corners, looking really good. It metacity (frame) do not work very well under GTK 3.8.x, therefore, they were replaced on the scope of topics GnomishDark.
The theme can work in any desktop environment on GTK, such as Gnome, Mate, Unity, Cinnamon and so on. If you want to get the Qt4 applications was a GTK style, run qtconfig-qt4, select GTK+ for 'Selected GUI Style' Appearance tab and will persevere.
Run in terminal:
sudo add-apt-repository ppa:noobslab/themes sudo apt-get update sudo apt-get install e17gtk-theme