If you take a look at the cards in signatures, they all seem so similar. The blues, the grays (or platinum for some) but really, the colors on the face of the cards don't seem to be all that unique. Yes, there are exceptions - the clear-ish, the reds, etc., but what would be truly different?
What would really set a card apart?
I think metal cards certainly turn the corner on the otherwise boring cards. And, of course, a contrasting edge. 