Have you ever needed to swap images for an menu?  You can use javascripts onmouseover  and onmouseout to make it happen

Just add the following code to your <img> tag

onmouseover="javascript:this.src='image url';"
onmouseout="javascript:this.src='image url';"

example:

<img src="on.jpg" onmouseover="javascript:this.src='off.jpg';"
onmouseout="javascript:this.src='on.jpg';">

Thats it your menu will now how the classic image rollover.