I am trying to find other large Coppermine galleries. Are there any lists of them anywhere?
No I don't think but you can search via google:
Powered by Coppermine there you can find thousands of coppermine gallerys.
See the thread Share your galleries (http://forum.coppermine-gallery.net/index.php/topic,22690.0.html). I would advise working backwards since the first posts are very old and may not still be online.