Hi! Thanks for your post, it helped me find the right place to insert my code (to retrieve the alt text) into the wp-tiles plugin. So here it is, just add this before your code..
$thumbnail_id = get_post_thumbnail_id( $post->ID ); $alt = get_post_meta($thumbnail_id, '_wp_attachment_image_alt', true);
and then you can go
alt='<?php echo $alt ?>'
Have a great day ??