[Kirk Y]

Find in "includes/class_bbcode.php":

function handle_bbcode_img_match($link)
	{
		$link = $this->strip_smilies(str_replace('\\"', '"', $link));

		// remove double spaces -- fixes issues with wordwrap
		$link = str_replace('  ', '', $link);

		return '<img src="' .  $link . '" border="0" alt="" />';
	}

Replace with:

function handle_bbcode_img_match($link)
	{
		$link = $this->strip_smilies(str_replace('\\"', '"', $link));

		// remove double spaces -- fixes issues with wordwrap
		$link = str_replace('  ', '', $link);

		return '<span class="post"><img src="' .  $link . '" border="0" alt="" /></span>';
	}

Now go into your AdminCP -> Styles and Templates Manager -> Choose Main CSS from the Style Dropdown.

Scroll down to Additional CSS Definitions and add this:

.post image{
	border-style:dashed;
	border-color:red;
	border-width:1px;
      }