My default application for images is ViewNoir: > xdg-mime query default image/jpeg viewnior.desktop But the first option in the "Open with" drop down is GIMP.
But once you select a different application, it'll be remembered for the next screenshots. Isn't that enough?
Well, remembering the last choice would be enough. But: currently it does not remember the last choice (version 1.9.1). The associated issue is still open: bug 13559.
Ok, so let's handle this in bug 13559, which I can't reproduce, please check my comment there.