Change the Gnome Menu Icon

1)open the terminal and type: gconf-editor

2)go to "apps" -> "panel" -> "objects"

3)Find the right object. Under "object type" it should say "menu-object"

4)Once you have found the right object, check the box that says "use-custom-icon"

5)Then right click where it says "custom-icon" and click "Edit Key"

6)type in the location of the icon and click ok.

7)Reset the tool bar. Type killall gnome-panel in the terminal.