Despite this being a sort of mood board for antagonist species confirmed for Destiny, I can't help but feel this concept ended up as the spider tanks/walkers instead. And as you said, some concepts don't make it into production. Though biped tanks along with multipeds might offer a bit of variety in the vehicular arena. As an aside, I'm getting a very Hoth probe droid vibe from that glacial city concept art board. Anyway, it's a more upright mech, sure, but doesn't resemble the one from the mood board apart from the vague resemblance of that back shielding, not in the apparent number of legs or the torso. We'll see which, or if either model end up in the game in any capacity, but my gut tells me the standing mech got scrapped for a Fallen spider tank, anyway.