According to the MDC, it is possible to assign an image on a radio button element.

As written in this page, the image attribute should correspond to the URL of the image you want to display.
If it works on menuitems, it displays absolutely nothing on my radio buttons.

2 solutions to avoid this problem :

- The best and easiest way is to replace the image attribute by src attribute (which actually does exactly what the image attribute is supposed to do)

<radio id="orange" label="Orange" src="chrome://skin/orange.png"/>

- More complicated solution is to give the radio buttons the class menu-iconic and set the image through the CSS using their background-image property.