Y por qué no utilizas esto ?
http://javascript.internet.com/image-effects/jas.htm
Que está aquí ?
http://www.robertnyman.com/jas/
Aunque ... lo que hace es esto, (pero mas extenso, con slideshow, etc):
Código:
<script language="JavaScript" type="text/javascript">
function onChange(src) {
var element = document.getElementById("bigone");
element.src = src;
}
</script>
<table border="1">
<tr>
<td colspan="4"><img src="1.jpg" alt="" name="bigone" width="320" height="240" id="bigone" /></td>
</tr>
<tr>
<td><img src="1.jpg" width="160" height="120" alt="" onmousedown="javascript:onChange('1big.jpg');" /></td>
<td><img src="2.jpg" width="160" height="120" alt="" onmousedown="javascript:onChange('2big.jpg');" /></td>
<td><img src="3.jpg" width="160" height="120" alt="" onmousedown="javascript:onChange('3big.jpg');" /></td>
<td><img src="4.jpg" width="160" height="120" alt="" onmousedown="javascript:onChange('4big.jpg');" /></td>
</tr>
</table>