$tabNomFichier = array();
while (...) {
  // ...
  $tabNomFichier[] = $uploadname;
  // ...
}

printf("<pre>%s</pre>\n", print_r($_FILES, 1));

Array
(
    [image] => Array
        (
            [name] => Array
                (
                    [0] => Active.jpg
                    [1] => 
                    [2] => 
                    [3] => 
                    [4] => 
                    [5] => 
                )

            [type] => Array
                (
                    [0] => image/jpeg
                    [1] => 
                    [2] => 
                    [3] => 
                    [4] => 
                    [5] => 
                )

            [tmp_name] => Array
                (
                    [0] => /tmp/php5710wx
                    [1] => 
                    [2] => 
                    [3] => 
                    [4] => 
                    [5] => 
                )

            [error] => Array
                (
                    [0] => 0
                    [1] => 4
                    [2] => 4
                    [3] => 4
                    [4] => 4
                    [5] => 4
                )

            [size] => Array
                (
                    [0] => 15540
                    [1] => 0
                    [2] => 0
                    [3] => 0
                    [4] => 0
                    [5] => 0
                )

        )

)

<?php

session_start();

if (isset($_SESSION['level']) && $_SESSION['level'] == 2)
{
}
else
{
$_SESSION['error'] = "3";
header('Location: ../../error.php');
}

require("../../includes/config.php");
require('../../includes/functions.tpl.php');

while(list($key,$value) = each($_FILES['image']['name']))
{
	if(!empty($value))
	{
	$filename = $value;
	//echo $_FILES[image][name][$key];    equivalent to    print "$filename<br>";
	$uploaddir = "../../gifts"; 

	$allowed_ext = array( 'jpg', 'gif', 'jpeg', 'png' );  
	
	
	$max_size = "50000"; 
	$max_height = "300"; 
	$max_width = "300"; 
	
	$upload = ''; 
	  
	
	//get the file's extension
	$ext = pathinfo($_FILES['image']['name'][$key]);
	$extension = $ext['extension'];

	//compare uploaded file with authorized extensions
		if (in_array($extension,$allowed_ext)) 
		{
		//check the file's size in kb
		if($_FILES['image']['size'][$key] > $max_size)
		{
		print "File '$key' size is too big!";
		$upload = false;
		}
		//check the file's	dimension WxH
		if ($max_width && $max_height) 
		{
		list($width, $height, $type, $w) = getimagesize($_FILES['image']['tmp_name'][$key]);
			if($width > $max_width || $height > $max_height)
			{
			print "<br>File '$key' height and/or width are too big!";
			$upload = false;	
			}
			
			//upload the file!			
			else
			{
			if(empty($upload) && is_uploaded_file($_FILES['image']['tmp_name'][$key]))
			{

			//create a random name for the uploaded file
			$date = date ("Ymd");
			$name = random_string();
			$uploadname = $date.'_'.$name.'.'.$extension;
			
			print "$uploaddir/$uploadname<br>";
			move_uploaded_file($_FILES['image']['tmp_name'][$key],$uploaddir/$uploadname);
			}
			}
						
		}





		}
	}
}
?>

je souhaiterais un _ plutot qu'un - dans le nom du fichier.

$uploadname = $date . '_' . $name . '.' . $extension; 

$_FILES['image']['size'][$key]
// et pas 
$_FILES[image][size][$key]