On your upload.processor.php page, the file name of the uploaded file can be retrieved with:
basename($uploadFilename);
You could add this to your redirect...
header('Location: ' . $uploadSuccess.'?img='.basename($uploadFilename));
...and then translate it to a full URL on the success page:
<?php
// filename: upload.success.php
// make a note of the current working directory, relative to root.
$directory_self = str_replace(basename($_SERVER['PHP_SELF']), '', $_SERVER['PHP_SELF']);
// make a note of the directory that will recieve the uploaded files
$uploadsDirectory = 'http://'.$_SERVER['HTTP_HOST'] . $directory_self . 'uploaded_files/';
?><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="stylesheet.css">
<title>Successful upload</title>
</head>
<body>
<div id="Upload">
<h1>File upload</h1>
<p>Congratulations! Your file upload was successful</p>
<p><?php echo $uploadsDirectory.$_GET['img'];?></p>
</div>
</body>
</html>