How do I add an icon of image to a menu button?

[B]

I have created a COM addin in C++ that adds a couple of
menuButtons(CommandBarButton) to Microsoft Outlook. I have used
commandBarButton->put_Caption() to put the caption on to the button.
Now, I would like to know how exactly would I be able to add an icon or
image to this particular button. Code snippets would be of great help.

Thanks,
B.