If you have an image type extra field and need to display a link directly to the image you must strip the default code that K2 uses to insert the image into it's foreach loop. You can insert this directly into your item.php override file.
<?php
$var = $this->item->extraFields->Image->value ;
$var = preg_replace('/<img src="/',"",$var);
$var = preg_replace('/" alt="Image" \>/'," ",$var);
echo '<a href="' . $var . "TextOfLink" . "</a>" ;
?>
Content management as it should have been in Joomla