I imagine something like this would do the job.
Code:
<script language="JavaScript" type="text/javascript">
var ic = 6;
var xoxo = new Array(ic);
xoxo[0] = "images/misc/banners/1.ico";
xoxo[1] = "images/misc/banners/2.ico";
xoxo[2] = "images/misc/banners/";
xoxo[3] = "images/misc/banners/";
xoxo[4] = "images/misc/banners/";
xoxo[5] = "images/misc/banners/";
function pickRandom(range) {
if (Math.random)
return Math.round(Math.random() * (range-1));
else {
var now = new Date();
return (now.getTime() / 1000) % range;
}
}
var choice = pickRandom(ic);
</script>