For the core "image" module, we really need a checkbox option for decorative images. So many large drupal projects with many contributors adding content are making the alt text "required to keep their sites accessible. By doing so, this forces screen readers to read alt text for every image that is placed on the site especially when they have no purpose.
By having a "decorative" checkbox for the required image alt field, it could be checked and create a null field. We need something obvious for limited permission content editors. Wordpress has this option with their accessibility plugin. It lets you check the decorative box and then leave the alt text box empty.
This is very important as drupal 8 has really come a long way with the accessibility and continues to do so. Our higher education sites depend on this. Thank you for doing such a great job so far!
