Es ist geschafft!! Hier der funktionierende Code, htaccess bleibt aussen vor!:
<?php
// Variable holen
$_GET["file"];
$_GET["path"];
$pathfile = $path."/".$file;
// Welcher Typ?
if (substr($file,-4) == ".gif") {$type = "gif";}
if (substr($file,-4) == ".jpg" or substr($file,-5) == ".jpeg") {$type = "jpeg";}
// Header senden
header("Content-type: image/$type");
header("Content-Disposition: attachment; filename="$file"");
@readfile($pathfile);
?>