I thought carefully on everyone's input and considered my goals and options. In the end I noted that only a minority of the images were actually larger than the display window, and several of those only by a small amount. Further, the really large images, in my opinion, don't require viewing at the original high resolution to be effective (these were mostly the technical illustrations).
To that end, I examined the .xml file and saw where to edit it to turn off dynamic image resizing. Then I turned to another CC app, the PixConverter, and batch-resized anything larger than the display window so it would fit without further resizing. Viola, everything is now displayed clearly, without the dreaded jaggies.
Janys, it's true that some of my images were originally created in vector format, but of course they had to be saved in a bitmapped format for web display. The good part is, as you note, they can be resized cleanly to any resolution first, before conversion.
Thanks again for all the comments, guys, I feel my archive gallery is the better for them.
"You can't be a real country unless you have a beer and an airline - it helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer." -- Frank Zappa
Visit Spinland Studios: http://www.spinland.biz