I had to use the set session value behavior to save the file name to a session variable.
after the image upload, add the following code:
<?php
if (!session_id()) session_start();
if($_SERVER["REQUEST_METHOD"] == "POST") {
$_SESSION["updFile"] = $WA_DFP_UploadStatus["WA_UploadResult1"]["serverFileName"];
}
?>
then in the email template i could add the link using the session variable:
<a href="http://www.mydomain.com/uploads/<?php echo $_SESSION['updFile']; ?>">click here</a>