Nerds being nerdy, I'd like to have access to EXIF data It occurs to me that a smallish menu bar might be caused to pop up à la the menu bar in iBooks (for instance).
This would definitely add value.
Such a toolbar might also contain a brightness control. As a rule, I keep i-devices at a fairly low brightness but I've been taught always to turn displays to maximum brightness when editing.
This is a nice-to-have, as there are other ways to adjust display brightness.