When I create a new custom post type I use a $labels array to summarize all that can be put in the 'labels' post type array, like so:

$post_types['ng_game'] = array(
'labels' => $labels,
'title' => __('Spiele'),
'public' => true,
'publicly_queryable' => true,
'menu_position' => 5,
'show_ui' => true,
'show_in_menu' => true,
'show_in_nav_menus' => true,
'query_var' => true,
'capability_type' => 'page',
...
);

But if add the menu_icon to the $labels array it is not interpreted, I have to add it somewhere between the above shown code.

This is just a remark as I found it a bit odd that menu_name could be added to the $labels array but menu_icon cannot.

Kind regards