I managed to put Picasa into the Launcher by dragging it from /usr/share/applications. Everything is OK, except the icon: I cannot have an icon on it. When dragging the application, it keeps its icon just until I lay it down on the Launcher. The icon disappears as soon as the app is anchored.
SOLVED!!! It was just a matter of editing my ".local/share/applications/picasa.desktop" with "gedit" and change the icon value. It had "gnome-panel-launcher" and I wrote the path to my favorite Picasa icon and ... voilà!