Most of this is part of the Codex:
<?php
$attachments = get_posts(array(
'post_type' => 'attachment',
'numberposts' => -1,
'post_status' =>'any',
// This is where you specify the ID of your private image page
'post_parent' => $private_page_id,
));
if (count($attachments)) {
// We have attachments
?>
<ul id="flexiselDemo3">
<?php
// Now we loop through them
foreach ($attachments as $attachment) {
?>
<li>
<?php echo wp_get_attachment_image($attachment->ID, 'full'); ?>
</li>
<?php
}
?>
</ul>
<?php
}
?>