i use this to display random banners at bottom of my phpBB site

Code:
<script language="JavaScript" type="text/javascript">
<!--
    // JavaScript to interpolate random images into a page.
    var ic = 4;     // Number of alternative images
    var xoxo = new Array(ic);  // Array to hold filenames
        
xoxo[0] = "http://design.unerror.com/index.html target=_blank><img src=http://design.unerror.com/forum/banners/banner-designuneror.gif border=0>";
xoxo[1] = "http://www.unerror.com target=_blank><img src=http://design.unerror.com/forum/banners/banner-unerrorcom.gif border=0>";
xoxo[2] = "http://www.unerror.net/index.php?option=com_mospjirc&Itemid=27 target=_blank><img src=http://design.unerror.com/forum/banners/banner-unerrorirc.gif border=0>";
xoxo[3] = "http://users.martlev.com/ target=_blank><img src=http://design.unerror.com/forum/banners/martlev.gif border=0>";




function pickRandom(range) {
if (Math.random)
return Math.round(Math.random() * (range-1));
else {
var now = new Date();
return (now.getTime() / 1000) % range;
}
}
// Write out an IMG tag, using a randomly-chosen image name.
var choice = pickRandom(ic);
// -->
and then whereever i want the random pic to appear (in my case foot of page)

Code:
<SCRIPT LANGUAGE="JavaScript">document.writeln('<a href='+xoxo[choice]+'</a>');</SCRIPT><br />
am sure you could add something similar into the footer code of your invision board system

v_Ln