@Photomode: Photomode simply hides the GUI so that you don't have the resources, minimap, etc on the pic (or saves you the time to edit them out) as well as removes limitations to the camera (normally the cam can't move off the map, but the best photos will probably be slightly off the map (the camera is at a slight angle).
@Highest Settings: Except some computers won't work well on highest settings without a superb graphics card, and shadows could be quite brutal.
@Another note: Make a custom tileset or edit an existing one to remove the fog. Fog is generally unnoticable at first, but when you zoom out, it becomes impossible to take a picture. You know XML so it should be no problem!