In this tutorial we will help you install GrayDay, a GTK3 gray theme for Ubuntu 11.10/12.04 that is compatible with Unity and Gnome Shell. Here is a screenshot of this theme under Ubuntu 12.04:
Open the terminal and run the following commands:
cd /tmp && wget -O GrayDay.tar.gz http://goo.gl/mbxWh
sudo tar -xzvf GrayDay.tar.gz -C ~/.themes
gsettings set org.gnome.desktop.interface gtk-theme 'GrayDay'
gconftool-2 --set --type string /apps/metacity/general/theme 'GrayDay'
You can install the AwOken icon theme with GrayDay as described here. Credits for GrayDay go here.