Mordrak & Ghost Knights

So, this is the first thing that grabbed my attention in the new book. So much so, that I'm planning on picking up a box or two of GKTs and maybe a Draigo to covert off of. I probably won't make a GK army but Ghost Knights = Win in my book. So that said, any suggestions on how to make those guys a bit more ghostly than just a light blue/green paint job?

Outside the blue/green paintjob I don't know a good way to do it. Maybe play around with some lighting effects.

I would start with a white basecoat and then wash them with either blue or green wash and see what that looks like. I think that is a unit that will just look sick painted up by someone who is really good.