In this tutorial we will seen another GTK3 theme named Darko that can be installed in Ubuntu 11.10 Oneiric Ocelot. This theme is based on Ambiance and can be integrated smoothly with the Unity interface.
Open the terminal and run the following commands:
wget -O darko.zip http://goo.gl/CqdFA
unzip darko.zip -d ~/.themes
Use GNOME Tweak Tool to enable Darko, or run the following commands:
gsettings set org.gnome.desktop.interface gtk-theme 'Darko'
gconftool-2 --set --type string /apps/metacity/general/theme 'Darko'
You can select an icon theme from here, which can render your theme more attractive.