I create the "start icon" for the ubuntu main menu. the preview image can be used directly, the download package is the GIMP format file.

installation

1. add a "Main Menu" to your panel
2. run gconf-editor
3. navigate to /app/panel/objects

find a object_x with the "object_type=menu-object".

(my main menu is "object_8")

4. tick up "use_custom_icon"
5. change "custom_icon" value to the image path.