go to home goods and look for lamps bigger in scale :)

i would consider getting mirrors for behind the night stands that are wide as nightstands and tall as bed. very plain and simple. matching. home goods has them.move pictures to side and add a trinket box. search arched beds, but i find it difficult to like things above an arched bed myself.

With your high arched headboard I also find it hard to like anything hung above them.

How about an open ornamental iron piece?

I was thinking something that spreads across the width of the bed.

It is hard to achieve a balance above the arch. My question to you is, if you add something above the bed, what about the space over the nightstands. My number one advice is to by larger lamps. I would hang art above the night stands perhaps two pictures over each night stand for height and have the bottom picture fall behind the lower lamp, somewhat. I would leave the space above the bed empty so that your attention is drawn to the beautiful design of the headboard.

something along these lines?

I wouldn't put anything above the bed, as the headboard is the focus, and instead do either mirrors or art on each side above the night stands.