i know you don't want to hear this, but, i wouldn't do it. you never know when some freak thing might happen.
Example: we had some windows in our house broken because of dynamite blasting at a quarry several miles away from our house. it seems that day they got the charge too near avein and it helped the aftershock of the blast travel further. Three windows broke and 2 pictures on a wall fell off. Nothing in DD's room, but it taught me that you just never know.
Is there another wall in your nursery that you could put the pictures on?