I really, really like the "rippled waves" D back design. It really captures the eye, it's very simple, not even on the level of Rider Backs for flash - which for this deck I think is a good thing, because we want people jazzed about the faces more than the backs. It's a pretty neutral design without being boring.
I liked the earlier version that had DISCOURSE running down from the left corners - keep that idea, but maybe use a more blue or purple shade. It would in essence look like an index running down from the left corner - in fans and spreads, I think it would look very cool. (Anyone got the chops to create a mock-up fan of this?)
Try to make the border thin - like "Tendril Deck" thin. I like a border, but I REALLY like a super slim border, because they make the fans look all the more attractive while also remaining a highly functional design.
And I have an overall suggestion for the front designs - vote me down if you think I'm wrong:
DON'T go into the bleed on the front designs. I have decks that have different bleed designs on them, and they look horrible and practically make it a marked deck. Leave at least a slight border, so the front patterns aren't edge-visible as well as to compensate for the front being slightly off-center in relation to the back - which nearly always happens at USPC.