Hi, Robert
As far as I know, all browsers besides Safari aren't set up to render tiff files by default. Are you using Safari to display the files in Galaxy?
There are extensions for Firefox and Chrome that will allow you to display these files. Would that be an option?
As a side note: creating, saving, and manipulating images and thumbnails would require Galaxy including a server side image processing library as a dependency. I'd like to do this at some point in the future as it would allow us other advantages too.
Thanks,
Carl