Some purple dark eldar glyphs would look really nice I think, on the front, following the dwarfs cover that is. I like the interior of the current codex, with the scary khaine face with the gaping mouth. I'm a particular sucker for those opening words "The Book of Immortal Evils". They're chilling and classy. Something like that wouldn't go amiss... Maybe just a bunch of pointy Commorrite spires on the cover would do the trick for me. But either way if it's nice enough, I probably will buy it.
Skin texture sounds metal, I'm into it.