Marples is a (gtk2/3) theme, for those who like dark themes. the name marples is derived and pays homage to Marp-1-blue theme by Malys777.
The theme is beta right now. The writer is working on the theme everyday, so it is coming along nicely.
1.) Download the theme: http://gnome-look.org/content/show.php/Marples-black?content=144240
2.) Right click on desktop and choose “Change Desktop Background”. In “Appearance Preferences” window “Theme” tab click Install button and select just downloaded theme to install.
3.) After installed Marples-black theme, select to apply it.