Edit box-header on WordPress Dashboard

I clearly didn’t know how to google, as this page already explains how to do exactly what I wanted. Adapting it a bit, for it to work with different post types, I came up with the following:

add_action('do_meta_boxes', 'replace_featured_image_box');  
function replace_featured_image_box()  
{   
    $post_types = array('bwps', 'page', 'post');
    foreach( $post_types as $post_type ) {
      remove_meta_box( 'postimagediv', $post_type, 'side' );  
      add_meta_box('postimagediv', __('Featured Image <small style="opacity: .6">500*500</small>'), 'post_thumbnail_meta_box', $post_type, 'side', 'low');  
    }
}