After looking into the fuse box thing a bit more I really started to doubt it. I don't know the exact dimensions of the box but considering the thickness of the wall, which is a bit too thick in the model by the way, I really doubt it would fit inside. Also the A deck level of the aft staircase apparently already has two fuse boxes so I don't think they would have needed a third one or even potentially 4 if the design would have been the same on the port side.
However I think it's safe to say now that there's something in the picture that is not previously discovered when you consider my point about the design of the panel. Another wild idea I had was that could've Titanic had the same layout as Britannic. I know it seems very unlikely but it works with what is seen in Browne's photo quite well. This would also explain the dark corner, I think.
The most mystic thing seems to be the object attached to the door. It seems to be too big to be a stop hook cleat but then again I cannot think of anything else it could've been. Maybe the upper knob of a dutch door but having that kind of door there doesn't make any sense for me. Maybe it could have been a foreign object?