Shmoo

Got it!

First remove thus line, it will remove the image from showing up at the back-end:

'menu_icon'  => 'http://example.com/post_type_icon.png',

After that add some custom CSS styling to the back-end, but you have to overwrite it very carefully!

Add this code to your functions.php file.

// Add custom Post Type icons ( CSS ) to back-end.
function custom_css_icons() {
	echo '<style type="text/css"> li#menu-posts-YOUR_POST_TYPE_LABEL_HERE a.menu-icon-post div.wp-menu-image::before { content: "\f127"; } </style>';
}
add_action( 'admin_head', 'custom_css_icons' );

This is your Post Type Label – don’t copy the ‘ ‘ symbols just the word.

$args = array(
		'label'               => 'YOUR_POST_TYPE_LABEL',   <----
		'description'         => 'Product information pages',

My CSS content: “\f127”; code will show a music icon but you can change it to any other default icon of the Dashicons Font by clicking on the icon at the following page and hit the ‘Copy CSS’ link.
http://melchoyce.github.io/dashicons/

Have fun!

But how can you explain this feature has never showed up before in earlier versions because I simply don’t have any customizable features activated , and while testing my themes without changing anything in 3.6 Beta it does shows up out of the blue.

And the worst part is it shows up empty, just a framework with nothing inside it.

Thanks for your help btw I really appreciate it.

For now I have hide-/removed it by a code snippet.

// Hide (sub) menuitems from the admin menu
function remove_submenus() {
  global $submenu;
  //Appearance Menu
  unset($submenu['themes.php'][6]); // Customize
}
add_action('admin_menu', 'remove_submenus');

Credits.
http://wpsnipp.com/index.php/functions-php/remove-all-admin-submenu-items/

Yeah I know this feature has been part of WP for some time but in the past i’ve always deleted it from the functions.php file because I don’t need it in my themes.

This code-snippet was always at the very end of the functions.php ( 2011 )

/**
 * Binds JS handlers to make Theme Customizer preview reload changes asynchronously.
 *
 * @since Twenty Twelve 1.0
 */
function twentytwelve_customize_preview_js() {
	wp_enqueue_script( 'twentytwelve-customizer', get_template_directory_uri() . '/js/theme-customizer.js', array( 'customize-preview' ), '20130301', true );
}
add_action( 'customize_preview_init', 'twentytwelve_customize_preview_js' );

If I deleted this code-snippet and also deleted the Google Webfonts, custom-headers and other stuff this ‘Customize’ menu-item was gone from the back-end.

Now at WP 3.6 Beta 2 I’ve done the same thing deleted all those scripts and code-snippets I don’t need from the functions.php ( 2013 ) but still the empty framework of the Live Editor is active in the menu.

That shouldn’t happen I believe.