[Gtk-sharp-list] Set custom icon for toolbar Button or MenuItem

[Stefan Saring]

Hi,

can anyone tell me how it's possible to set a custom icon (e.g. a 24x24
PNG image) for the Button's in the application toolbar and for
MenuItem's ?
I have not found such a property in the documentations. In glade it's
only possible to use the stock icons, but I don't need them.

Thanks,
Stefan