Install Opal Smooth Inset theme on Ubuntu 12.10 Quantal/12.04/11.10/Mint (Gnome Shell 3.6/3.4/3.2)

Install Opal Smooth theme on Ubuntu 12.10 Quantal/Ubuntu 12.04 Precise/Ubuntu 11.10/Linux Mint 13/12 for Gnome Shell 3.6

Opal Smooth Inset theme is actually Black Opal distro theme and extracted from Opal Distro, This theme is really looks cool. Opal Smooth theme is available for Gnome Shell 3.6/3.4/3.2 versions. Maybe this theme has some bugs in Gnome Shell 3.6 but I haven't notice any bug yet.
Here is Black Opal Distro for 64-bit.
You can use these Tools to change theme and icons: Gnome Tweak Tool, Ubuntu Tweak

Download Black Opal Distro Wallpapers
Install Opal-ACYL Icons

Opal Smooth Inset Gnome Shell Theme

Opal Smooth Inset theme tested on Gnome Shell 3.6/3.5/3.4 and available for Ubuntu 12.10/12.04/11.10

To install Opal Smooth Gnome Shell theme on Ubuntu/Linux Mint open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal:

Terminal Commands:
sudo add-apt-repository ppa:noobslab/themes
sudo apt-get update
sudo apt-get install opal-smooth-inset-3.4

That's it

Source: Black Opal Distro