In the latest GNOME 3, changing the theme isn’t as easy as you’re used to. Using Gnome Tweak Tool you can change the GTK theme but how about the titlebar (Mutter/Metacity theme)? Read on!
How to change GNOME3 GTK theme
To change the GTK theme in GNOME 3 (with or without GNOME Shell), you can use Gnome Tweak Tool which is available in the GNOME 3 Ubuntu PPA, Fedora 15 official repositories, etc. If you’re using Ubuntu 11.04 and the GNOME 3 PPA, run the following command to install it: