Register some bogus post types with icons.

plugin.php

<?php
/**
 * Plugin Name: Register Some Post Types
 */
add_action( 'init', 'my_register_post_types' );
function my_register_post_types() {
	register_post_type( 'cpt-1', array(
		'label' => 'Image',
		'public' => true,
		'show_in_menu' => true,
		'menu_icon' => 'http://0.gravatar.com/avatar/8585b20b69e8ff4b0ba737accfdbb31b?s=50',
	) );

	register_post_type( 'cpt-2', array(
		'label' => 'Sprite',
		'public' => true,
		'show_in_menu' => true,
		'menu_icon' => array(
			'image_url' => admin_url( 'images/menu.png?ver=' . time() ),
			'background_position' => '-359px -33px',
			'background_position_hover' => '-359px, -1px',
		),
	) );

	register_post_type( 'cpt-3', array(
		'label' => 'Sprite 2x',
		'public' => true,
		'show_in_menu' => true,
		'menu_icon' => array(
			'regular' => array(
				'image_url' => admin_url( 'images/menu.png?ver=' . time() ),
				'background_position' => '-359px, -33px',
				'background_position_hover' => '-359px -1px',
			),
			'2x' => array(
				'image_url' => admin_url( 'images/menu-2x.png?ver=' . time() ),
				'background_size' => '390 64',
			),
		),
	) );
}