As you know I have been playing around with Ubuntu 12.04 lately. I found this article on creating custom launchers and Quicklists for Ubuntu unity. Being able to customize the main interface is key to any operating system. That has not always been an easy thing to do in Linux.
In the article it looks fairly easy to customize entries for specific applications. However I'm not sure you can customize an icon to launch random applications, but I intend to look into that. Anyway there are a lot of examples here you can work from and it's a very informative article.