function new_post_thumbnail_meta_box() {
global $post; // we know what this does

echo ‘<p>Content above the image.</p>’;

$thumbnail_id = get_post_meta( $post->ID, ‘_thumbnail_id’, true ); // grabing the thumbnail id of the post
echo _wp_post_thumbnail_html( $thumbnail_id ); // echoing the html markup for the thumbnail

echo ‘<p>Content below the image.</p>’;
}
function render_new_post_thumbnail_meta_box() {
global $post_type; // lets call the post type

// remove the old meta box
remove_meta_box( ‘postimagediv’,’post’,’side’ );

// adding the new meta box.
add_meta_box(‘postimagediv’, __(‘Featured Image’), ‘new_post_thumbnail_meta_box’, $post_type, ‘side’, ‘low’);
}
add_action(‘do_meta_boxes’, ‘render_new_post_thumbnail_meta_box’);