There are plenty of dark themes available for Gtk, most popular packs like Ambiance-Blackout and so on. Ambiance Dark Blue theme is another great dark version with combination of blue/teal color. As we tested this theme also delivers best user experience, if you are one of those who don't like bright themes because bright light hurt eyes then you should give a try to this theme. It is compatible with Ubuntu 14.10 Utopic/Ubuntu 14.04 Trusty (we didn't tested for GTK 3.16 but hopefully it will work just fine) and it works under Unity, Cinnamon, Mate, Gnome Fallback, and Xfce expect title bar in Xfce. If you enounter any bug within this theme then report it. Ardis icons used in following screenshots. You can use Unity Tweak Tool, Gnome-tweak-tool or Ubuntu-Tweak to change themes/icons.
