Here are 5 awesome themes for Ubuntu downloaded from gnome-look.org.
To install a theme watch the ubuntorial (theme used: Cabal)
Archiplex-Blue+Dark Download Here
When downloaded extract the Archiplex_Blue_Dark_by_elleti_brainvision file to your Desktop and install it.
Cabal Download Here
Lagadesk-Turquoise Download Here
When downloaded extract the files to your Desktop to install the GTK theme open the GTK+Metacity folder and install the LaGaDesk-Turquoise.tar.gz file. When using Emerald there is also a Emerald version and there is a wallpaper you can use.
Lithium Download Here
Download and extract the files to a folder on your Desktop to install the GTK theme install the Lithium.tar.gz file. If you use Emerald you can import the Lithium.emerald file.
Win2-7 3.1 Download Here
Download the theme pack and extract it in your Downloads folder, open a Terminal (Applications -> Accessories -> Terminal) and copy+paste the following line: ./Downloads/Win2-7\ Pack/install.sh
For more themes/eyecandy visit: gnome-look.org
For the newest Win2-7 pack (v6.4.3) All you need to do is extract the archive and double click on GUIInstall.sh and click “Run in Terminal”.