you can't unless you move the button on top of that image...
Maybe you should explain what you gonna do?
... or, you could respond to a click event on the image (I'm assuming you're using a picture indicator), get the coordinates, find out if they're within the rectangle of the button, and then trigger the button's click event.
Sounds to me like Lynn's suggestion is far easier.
... or you can also customize a button with your image. Even having two images depending if button is pressed or not.
Olivier L. | Certified LabVIEW Developer