If I figure out the full magical incantation, I'll post it :-), for the time being I'll leave off sacrificing and burning the black rooster. (Them thing's good eatin')
Basically, one has to make the change in LocalSettings.php as noted, place all of the images to be included at the _top level_ of the 'images' subdir, and then run "php rebuildImages.php --missing". This appears to load all of the images in the top level of "images" into the database.
The problem is that links to these images sometimes, but not always, work. This may partially depend on whether the link is added before or after the image is added to the database, but I haven't been able to establish any definite link. Basically, I've seen three different types of behavior:
1) Link works fine. 2) Link points to file of MIME type image/jpg (or whatever it is), but there is a message something like "no log entry", and the image does not appear on the page, just the link. 3) Link does not point to anything (i.e. points to empty page).
Some of my image names contain "__" (double underscores), and all of them contain single underscores; I've tried getting rid of the underscores, but again, that does not seem to have an effect, and the documentation for MW indicates that the _ character has no special meaning (though it normally appears as " " in link names).
So I guess I'm going to have to explore the other scripts Rob mentioned, and possibly other approaches. We want to have this site up by the 29th, so want to have it available for internal testing in the next five days or so, so time is getting tight. I confess, I hadn't expected the task to be quite so difficult. (I'm converting from MoinMoin, and while it doesn't have nearly the power of MW, there's one thing I'll say about a flat file database structure; it's _dead easy_ to write scripts to manipulate content in just about any way one could want :-) )
Cheers, Ken