siva-flat-themes (GTK2|GTK3 themes).

Siva Flat Themes for gtk3, gtk2, metacity, unity, xfwm4, openbox and emerald. There is 8 versions of themes.

Requirements for gtk3 theme is gnome-themes-standard and gtk-engine-unico.
Requirements for gtk2 theme is gtk-engines and gtk-engine-murrine.

Optional dependencies: gtk-engines, murrine, gtk-engines-unico.