On "open" blogs like vari.antville.org, users can not access images/all,
while /galleries is open to everyone on blogs set as "open" or even "public".

I suggest opening the list of uploaded images on "open" blogs to all
registered users (or to all subscribers) - and restricting access to
/galleries on "public" blogs to owners and content managers because it
isn't easy to guess that tagging an image makes it easy to be found by
other people.
(Maybe /galleries/somegallery shouldn't stay accessible to everyone, too.)