Not sure, but give it a try :)
<div>
<a href="tom.jpg">
<img src="http://www.wmagency.co.uk/wp-content/uploads/2011/04/test.jpg">
onmouseover='document.getElementById("table_id_here").style["background-image"]="url(\'jerry.jpg\');'
width="72" height="54" alt="" />
</img></a>
</div>