Currently, dplcache is defined in DPLMain.php to be placed in the images folder, which is both unusual and arbitrary. They're not images, they're cache files. This location creates various headaches. Ideally, a better home would be, maybe... $IP/cache/dplcache ? :)

global $wgUploadDirectory, $wgRequest;
if ( $DPLCache != '' ) {
        $cacheFile = "$IP/dplcache/$DPLCachePath/$DPLCache";