Assuming that you want to be able to open the windows, I can think of a couple of ideas:
1) I've seen semi-transparent paper that can be applied to the glass. It would let in light, but you wouldn't see the brick wall.
2) You could mount small shades or blinds to each window that would swing out when you open the casement, but you could roll up whenever you wanted to look at the brick wall. I'm not certain where you could find something like that.