something else to keep in mind...

with basic inline javascripting, you can do something like this:

<img src="image.png" style="cursor: pointer;" onmouseover="this.src='imageb.png'" onmouseout="this.src='image.png'" />

onmouseover="this.src='imageb.png'" is used to change the image on hover
onmouseout="this.src='image.png'" is used to change it back to the original