Customized quick acces toolbar - adding images to macro buttons

Hello,

I am trying to add images to the macros available on the quick access toolbar -- attached is a workbook in which I have added 4 do-nothing macros to the quick-access toolbar.

I'm not sure if they will show up for everyone the same way...so I included an image of that portion of the toolbar.

QUestion: How do I add a helpful image to the button to replace the default button image? I would like the user to intuitively know which button to mouse-over to launch the different macros.

Thank you