functions.php

<?php
// Add this to your theme's functions.php
// This filter will insure that the wp-image-{IMAGEID} class is added to your 
// image tags, allowing media cloud to work more optimally
add_filter('wp_get_attachment_image_attributes', function($attrs, $attachment, $size) {
    if (!empty($attachment) && isset($attrs['class'])) {
        $attrs['class']  .= ' wp-image-'.$attachment->ID;
    }

    return $attrs;
}, PHP_INT_MAX, 3);