I'm currently updating the plugin Media Credit for 3.9 and I really like the new Edit Image modal in TinyMCE. However, there is currentyl no way to add custom fields to the modal (like attachment_fields_to_edit/attachment_fields_to_save). I know I can provide a whole new template via the action hook, but all I really want to do is add two fields. So a few filter hooks in
media-template.php would be really nice.