Thought about the pics and an art light just to put some light down at that end.

Yeah -- unless there's a window behind the photographer, the mirror will just be dark and make the person climbing the stairs self-conscious. Pictures will give them something to look at as they progress...

To me there is no question that you should hang art. The last thing anyone would want is to watch themselves head on walk down that hallway.

Yes the art work for sure,

Pictures.

At first I was going to say the pictures/photos but the mirror might be an interesting choice. I would try each out by at least propping each up on top of the cabinet and living with it for a few days (although I'm sure you will know almost instantly which is a better choice).

Pictures. The mirror shown doesn't have enough personality and contrast to coordinate with the chest.