Lower the picture about 10" as it's way too high. Hang some more pictures or other art work where you have room.

How about painting the doors? I think it would give it a pop of color without having to paint all of your walls.

I agree with Nina, painting the doors is going to be a huge help. Trade up on the door hardware from the current knobs to something a little more substantial. Since the ceiling looks as if it is pitched why not make this a point of interest? Add a half-round or picture frame molding to the ceiling running up the sides and ends of the hallway. Put the molding about 4" in from the crown so you now have a rectangle on your ceiling. Paint the molding the same as your current trim but paint the inside section in a really light blue.

Maybe a small pretty chandelier?

I think the hallway looks boring because the doors look boring. Change the doors to white 6-panel doors. Run a white chair rail the length of the hallway. Perhaps install white beadboard on the lower half of the wall to lighten things up.