Dyne gtk3 theme came out yesterday from the hands of thrynk. It is a very elegant theme that uses optically simple elements to give a silk result. As you can see Dyne is easy on the eye using grey and dark shades in general. It only works for GTK 3.4 and you got to have gtk2-engines, gnome-themes-standard and gtk3-engines-unico installed.

Dyne gtk3