About your problem, i think you forgot activate "use shots" in mydownloads config panel.
I've found a bug, users can't upload shots.
Just add this to submit.php:
After line
include_once XOOPS_ROOT_PATH . '/modules/' . $xoopsModule->dirname() . '/class/mimetype.php';
Add
include_once XOOPS_ROOT_PATH . "/class/uploader.php";