To make the top panel of Ubuntu 12.04 become transparent, you can use the popular tool Compiz Config Settings Manager. Compiz is in fact a very powerful tool for tweaking, you can use it to set up and customize many things in Ubuntu 12.04. In today's article, I will focus only about how to make the Ubuntu panel transparent.
First of all you need Compiz Config Settings Manager since it is not pre-installed in Ubuntu 12.04 by default. You can either search for it in the Software Center of Ubuntu or run the following command:
sudo apt-get install compizconfig-settings-manager
After Compiz is installed, you just need to launch it. Hit the super key (the window key) to open Unity then search for Compiz. You will see the Compiz icon appearing immediately, click on it to launch Compiz. Next, select the Desktop category on the left side of the Compiz window:
On the Desktop tab, choose Ubuntu Unity Plugin
Next, select the Experimental tab
On that Experimental tab, you will se the "Panel Opacity" option. You just need to change the value of opacity ( choose 1 for absolutely no opacity and 0 for totally transparent) and the opacity level of the Ubuntu panel will be adjusted according to the value you choose: