You can do it with Javascript.
Sample script:
<script>
function showDialog(url, w, h, resize)
{
var dialogWidth = w;
var dialogHeight = h;
var dialogLeft = (screen.width - dialogWidth) / 2;
var dialogTop = (screen.height - dialogHeight) / 2;
var imageWin = window.open(url,"_blank",(resize ? "resizable=yes,scrollbars=yes," : "") +
"height="+dialogHeight+",width="+dialogWidth+",top="+dialogTop+",left="+dialogLeft);
return(imageWin);
}
function showImage(url)
{
var winHandle = showDialog("", 500, 500, true);
if (winHandle)
{
var html = "<html><body><p align=\"center\"><img src=\"" + url + "\"></p></body></html>";
winHandle.document.write(html);
}
}
</script>
Sample hyperlink:
<a href=" void(0)" onClick="showImage('http://www.dotnetnuke.com/Portals/_default/Skins/DNN-Minimal/images/dotnetnukelogo.gif')">[Thumbnail]</a>
Nik