Admin Bar Buttons

Is there a way to add icons to custom links in the admin bar? I have been searching around for a while now, with no results.
Is it maybe possible to add some lines to this function code so it shows images as buttons:

<?php
add_action('admin_bar_menu', 'add_toolbar_items', 100);
function add_toolbar_items($admin_bar){
	$admin_bar->add_menu( array(
		'id'    => 'my-item',
		'title' => 'My Item',
		'href'  => '#',
		'meta'  => array(
			'title' => __('My Item'),
		),
	));	

}
?>

[Please post code or markup snippets between backticks or use the code button.]