Try this:
1) Edit ./includes/class_bbcode.php
2) Search:
PHP Code:
$templater = vB_Template::create($this->printable ? 'bbcode_quote_printable' : 'bbcode_quote');
3) Before add:
PHP Code:
if ($this->contains_bbcode_img_tags($message))
{
$message = preg_replace('#\[img\]\s*(https?://([^<>*"]+|[a-z0-9/\\._\- !]+))\[/img\]#iUe', "\$this->handle_bbcode_url(str_replace('\\\"', '\"', '\\1'), '')", $message);
}