Re: TikiWiki 3.2 - Image vs File Galleries confusion
I can't find a way to specify thumbnail size in file galleries in 3.2 either, so if you need to do that, then I guess you better stay with image galleries.
The guy who has been developing the file galleries most, Nyloth, asked on the dev list for input on features for them; I'm not sure if thumbnail size was mentioned or not. This would be good to have (again). You could submit a feature request at http://dev.tikiwiki.org.
-- Gary