Function to get custom post image URL

Can you show us what the cp_get_image_url() function does?
Is it from a plugin or theme?

Is the image uploaded to the Featured Image or a Custom Field?

Without knowing what that function is actually doing, the best I could come up with is this:

<?php
    $media = get_attached_media('image');

    foreach($media as $m) {

        $mee = wp_get_attachment_url($m->ID);

        echo $mee;

    }
?>

This will get all images attached to the Post. So you might end up with a couple of URLs