bueno aqui esta terminado:
<script type="text/javascript" src="/javascript/jquery.js"></script>
<script language="JavaScript" type="text/javascript">
<!--
function randomize(codigo){
var rand = Math.floor(Math.random() * 3);
$("#changeme").attr('src','http://img.youtube.com/vi/'+codigo+"/"+rand+".jpg");
}
//-->
</script>
<?php
function ObtenerFoto($codigoVideo, $numFoto) {
$path = "http://img.youtube.com/vi/";
echo '<img src="'.$path.$codigoVideo.'/'.$numFoto.'.jpg'.'" id="changeme" onmouseover="randomize(\''.$codigoVideo.'\')" />';
}
ObtenerFoto('j455fwdaUJM', 1);
?>