I am using awesome with on ubuntu 12.04. I changed the theme with myunity Now my Gnome applications are presented white and all other in the dark theme. Why ?
The theme was not set, so you get a ugly look.
Basically there's two options, set a default GTK2 (~/.gtkrc-2.0) and GTK3 (~/.config/gtk3/settings.ini) theme, or simply launch the settings daemon, IIRC