Here i will tell you how to add new icons to ubuntu in an easy way…
you can download the icon files from ubuntu artwork site or gnome-look.org and going to ubuntu icons tab…..or by going to the below link directly….
http://ubuntu-art.org/index.php?xcontentmode=8125
extract the downloaded folder…Then go to your home folder then press ctrl+H simultaneously….then you can see some hidden folders…search for .icons folder and paste the extracted icons folder here….
Then go to your desktop>rightclick>select change desktop background
Then select themes tab…select customize from lower right corner near install and in the new window opened select the folder from icons tab…