I guess this topic is more about Ubuntu and creating a launcher, than about GIS.
You can find a detailed explanation about creating a launcher at the Ubuntu Community Help Wiki. The main part is a .desktop file you can create anywhere (for example your Desktop), which you can add to the Ubuntu launcher. An example for the file would be:
[Desktop Entry]
Version=0.10
Name=TileMill
Comment=This is my comment
Exec=/home/path/to/tilemill/index.js
Icon=/home/path/to/tilemill/tilemill.ico
Terminal=false
Type=Application
Categories=Utility;Application;
After creating and saving that file, make it executable in the terminal or right click the icon - go to Permissions tab - and check the "Allow executing the file as program".
To get it also to Unity Launcher copy/move the file to /usr/share/applications/
or ~/.local/share/applications/
Worked for me on Ubuntu 12.04 and I guess it will work also on 13.10