Wrapping Featured Image on Add/Edit Page in div?

When you post this question @PontusAbrahamsson answered you with a good function:

function wpse_111428_change_feature_image_admin( $content ) 
{
    global $post;
    $size = 100;

    $id = get_post_meta( $post->ID, '_thumbnail_id', true );

    if( $id )
    {
        return wp_get_attachment_link( $id, array( $size, $size ) );
    }
}
add_filter( 'admin_post_thumbnail_html', 'wpse_111428_change_feature_image_admin' );

just replace it with a modded version that use code taken from \wp-admin\includes\post.php:

function wpse_111435_change_feature_image_admin( $content, $post_id = null )  {

  $size = 100; // set here your size

  $thumb = $post_id ? get_post_meta( $post_id, '_thumbnail_id', true ) : false;

  if( $thumb ) {
    $set_thumbnail_link = '<p class="hide-if-no-js"><a title="' . esc_attr__( 'Set featured image' );
    $set_thumbnail_link .= '" href="https://wordpress.stackexchange.com/questions/111435/%s" id="set-post-thumbnail" class="thickbox">' . __( 'Set featured image' ) . '</a></p>';
    $upload_iframe_src = esc_url( get_upload_iframe_src('image', $post_id ) );

    $content="<div id="draggable" class="ui-widget-content"><p>" . __('Featured Image Code') . '</p>'; // your html

    $content .= wp_get_attachment_image( $thumb, array( $size, $size ) ) . '</div>'; // this one output the image

    $content .= sprintf( $set_thumbnail_link, $upload_iframe_src );
    $ajax_nonce = wp_create_nonce( 'set_post_thumbnail-' . $post_id );
    $content .= '<p class="hide-if-no-js"><a href="#" id="remove-post-thumbnail" onclick="WPRemoveThumbnail(\'' . $ajax_nonce . '\');return false;">';
    return $content . esc_html__( 'Remove featured image' ) . '</a></p>';
  }

  return $content;

}

add_filter( 'admin_post_thumbnail_html', 'wpse_111435_change_feature_image_admin', 20, 2 );