You can do that within the loop using wp_get_attachment_image
.
Something like (not tested):
//loop starts
//values for get_posts ( or wp query if you prefer)
$args = array(
'post_type' => 'attachment', //gets the attachments aka your images
'numberposts' => -1,
'post_parent' => $post->ID
);
// some attributes you want added to each image
$default_attr = array(
'class' => "background-attachment", //for your javascript
'alt' => 'something',
'title' => ''something
);
//loops through the attachments,
//uses the 'full' parameter assuming you want the default large image
$attachments = get_posts($args);
if ($attachments) {
foreach ($attachments as $attachment) {
echo wp_get_attachment_image($attachment->ID, 'full', false, $default_attr);
}
}
//loop ends
//your javascript for full page background via wp_enqueue_script