The ability to add/remove fields in the Gallery settings screen.
You are able to add fields to the media box with:
add_filter( 'attachment_fields_to_edit', <function>, null, 2); add_filter( 'attachment_fields_to_save', <function>, null, 2);
It would be great if you could also customize the Gallery settings in the same way to add settings specific to the theme. For instance, I have multiple styles for a gallery and I like the user to be able to easily pic the style it wants for that specific gallery for that specific page.
However, if my theme doesn't support columns in the gallery, I like to be able to remove that options not to confuse the user.