When I open a picture (in the default XUbuntu image viewer which is Ristretto) I expect to be able to navigate through all the other pictures in the directory pressing back/forward. But this doesn't work in Ristretto. I've set "open entire folder on startup" in the settings but nothing changed. I can remember that in the past selecting all the pictures in the directory instead of one to open could do the trick, but now there is no difference - back/forward buttons are always disabled.
Ivan, the navigation buttons (and the slideshow button) are active if you first open Ristretto, then Open the folder of interest from within Ristretto.