This is a Metacity theme I have made based on:
Natural Metacity mockup - http://gnome-look.org/content/show.php/Natural+metacity+-+Mockup.?content=120245
Gnome Natural theme - http://gnome-look.org/content/show.php/Gnome+Natural?content=122153.
Natural Moocow theme - http://gnome-look.org/content/show.php/Natural+Moocow?content=132788.

In the first screenshot there is a focused and unfocused window and in the second screenshot there is their highlighted states.

It is customizable
Since not everybody will like the orange highlights of this theme I have added all the images with orange parts in a folder inside the theme. They are in GIMPs xcf format with layers easily customizable to any color you like :^) .

Once modified you can save them into the metacity-1 folder as .png and they will appear as windows decorations on your next login or theme change.

Suitable GTK theme
I recommend using this Metacity theme with any GTK theme with a dark menu bar. In order to match the menu bar with the window title bar you should set the background of the menu bar to #575757.
In the screenshots I used the GTK theme "Victory (Strikes Again)" - http://gnome-look.org/content/show.php/Victory+%28Strikes+Again%29?content=123936.

Enjoy!

Update 1.1: Changed the inactive window look.