It's a decent idea, but yeah I think the reason it was never done was because of the concerns about some of the complaints we receive regarding images.. just better if we don't show explicitly when it was uploaded.
With that said, if it does have an image comment from, say, 2003 .. then it's pretty obvious anyway.
As for the dynamic gallery, that was always something I wanted fixed too, but at the time revert and darkklown showed me just how much work would be involved in sorting it out.. think "re-write most of the site's code" levels of work