Using WordPress 3.8 Icons for your Custom Post Types

admin-head.php

<?php

function add_menu_icons_styles(){
?>

<style>
#adminmenu .menu-icon-events div.wp-menu-image:before {
  content: '\f145';
}
</style>

<?php
}
add_action( 'admin_head', 'add_menu_icons_styles' );

admin.css

#adminmenu .menu-icon-events div.wp-menu-image:before {
	content: '\f145';
}

events.php

<?php

function create_events_cpt() {
  register_post_type( 'events', 
    array(
      'public' => true,
      'has_archive' => true,
      'menu_position' => 5, // places menu item directly below Posts
      'menu_icon' => '',
      'labels' => array(
        'name' => __( 'Events' ),
        'singular_name' => __( 'Event' ),
        'add_new' => __( 'Add New' ),
        'add_new_item' => __( 'Add New Event' ),
        'edit' => __( 'Edit' ),
        'edit_item' => __( 'Edit Event' ),
        'new_item' => __( 'New Event' ),
        'view' => __( 'View Event' ),
        'view_item' => __( 'View Event' ),
        'search_items' => __( 'Search Events' ),
        'not_found' => __( 'No Events found' ),
        'not_found_in_trash' => __( 'No Events found in Trash' ),
        'parent' => __( 'Parent Event' ),
        ),
    )
  );
}
add_action( 'init', 'create_events_cpt' );