Add image size to edit pulldown

functions.php

add_filter('image_size_names_choose', 'my_new_image_sizes');
function my_new_image_sizes($sizes) {
	$addsizes = array(
		"my-new-size" => __( "My New Size")
	);
	$newsizes = array_merge($sizes, $addsizes);
	return $newsizes;
}