[Lizard King]

class_bbcode edit :

	return '<img src="' .  $link . '" border="0" alt="" class="imageresize" onload="resize_image(this, \'' .  $link . '\', 540);" />';

vbulletin_global.js edit

* @param	string	Image object
* @param	string	Image link
* @param	integer	Image max width
*/
function resize_image(obj, link, maxwidth)
{
	if (obj.width > maxwidth)
	{
		obj.style.cursor = 'pointer';
		obj.style.width = maxwidth + 'px';
		obj.style.height = parseInt(obj.height * maxwidth / obj.width) + 'px';
		obj.onclick = function()
		{
			window.location.href = link;
			return false;
		};
	}
}

and the css

.imageresize      {
        text-decoration: none;
        padding : 4px;
        border : 4px solid #eeeeee;
        max-width: 540px; width: expression(this.width > 540 ? 540: true);
}