To change the looks of Ubuntu 11.10 you need to install the gnome tweak tool. Gnome tweak tool is a tool to customize advanced GNOME 3 options.
To install gnome tweak tool open your software center and type: gnome tweak tool in the search field. Click on the search result and click on the Install button (or on the More Info for a short description), enter your password and when installed close the software center. To start gnome tweak tool press Alt+F2 and type: gnome-tweak-tool
Features:
Install and switch gnome-shell themes
Switch gtk/icon/cursor themes
Switch window manager themes
Gnome Tweak Tool allows you to change:
The user-interface and titlebar fonts
Icons in menus and buttons
Behavior on laptop lid close
Shell font size
File manager desktop icons
Titlebar click action
Shell clock to show date
Font hinting and antialiasing
Read more about Gnome Tweak Tool