I'm using Debian Jessie 64-bit with Gnome 3.14.1.

My TIF image files are opening by default in the PDF Viewer, don't ask why. In Nautilus, I right-click on the file, click Open With|Other Application...

[![Select Application window][1]][1]

If I right-click "Image Viewer", there is only "Forget association".

Where is the "create default association" button?

EDIT

I've found a ~/.config/mimeapps.list, which contains

    image/tiff=eog.desktop;

It seems that something else is overriding this configuration.

  [1]: https://i.stack.imgur.com/zkSIQ.png