As @sstangl suggested in #2888, when the image in the lightbox takes a while to load,
It would be useful to:
- Display something more meaningful than a black screen -- possible a spinner, that a background download is in progress?
This'll be somewhat less common in the medium term as we roll out server-side thumbnailing, but still a fairly common case when people are on slow network connections.
This is a polish feature that would be nice to add.