Re: Image Gallery phased out in future.
I activated the "Last files" module at this site briefly to test, and images in the file galleries have a "/preview123" kind of url. The image displays when the file name is clicked. (It displays in a popup colorbox when the module is in the center column, or in a new window when the module is in a side column.) This is in the most recent Tiki version (Tiki 5 alpha). I don't know off hand if the behavior is the same in Tiki 4 or 3, or why your site is acting differently.
-- Gary