Customizes the media edit modal.

customize-mediamodal.php

<?php 
/**
 * Implements hook_element_info_alter().
 */
function mymodule_element_info_alter(&$type) {
  if ($type['media']) {
    $type['media']['#attached']['js'][] = array(
      'data' => array(
        'media-file-edit' => array(
          'modalSize' => array(
            'width' => 0.7,
            'height' => 0.7,
          ),
          'modalOptions' => array(
            'background-color' => '#000',
            'opacity' => .55,
          ),
        ),
      ),
      'type' => 'setting',
    );
  }
}