Display post images randomly

Hi friends. First post, hopefully of many —

I’m trying to get these images to show up in a random order, I would even be happy if I could get them to show up by date. Right now they only show up with the most recent ID displaying first.

<?php
		$entry_class = 'show';
		if ( '' != get_the_post_thumbnail () ) {
			the_post_thumbnail();
			$entry_class = 'hide';
		}

				else {
			$images = get_children( array( 'post_parent' => $post->ID, 'post_type' => 'attachment', 'post_mime_type' => 'image', 'orderby' => 'menu_order', 'order' => 'ASC', 'numberposts' => 999 ) );
			if ( $images ) {
				$image = array_shift( $images );
				$image = wp_get_attachment_image_src( $image->ID, 'mixfolio-featured-thumbnail' );
				echo '<img src="' . $image[0] . '" class="wp-post-image"/>';
				$entry_class = 'hide';
			}

			else {
				echo '<img src="' . get_stylesheet_directory_uri() . '/images/image.jpg" class="wp-post-image"/>';
			}

		}
	?>

Originally I tried changing the following:

'orderby' => 'menu_order', 'order' => 'ASC',

but regardless of what options I put in there, it still shows up the same.

Any thought?

Thanks.