With the upcoming Hearthstone expansion: Whispers of the Old Gods, the OGs themselves are each getting representation as a Legendary Minion. Everyone who plays will automatically get C'thun and a pair of associated cultist cards (because C'thun relies on building a deck around him, they don't want you getting a bunch of useless C'thun cards without the guy himself.)
Of course, the exciting news is that this means that we're finally getting a good look at the two Old Gods we haven't seen in-game before, N'Zoth and Y'Shaarj. And much as I suspected during an earlier post, the image of N'Zoth has already been revealed (though we don't know what its card will be like mechanically, other than that it will cost 10 mana.)
UPDATE: The full art is below the rest of the post.
While C'thun was the eye-covered one and Yogg-Saron was the mouth-covered one, this guy isn't ears or noses or anything like that. But you know what he does look like? A freaking octopus. One of the big threats in Cataclysm that we never truly dealt with was Ozumat. In fact, Vashj'ir was filled with weird cephalopod monsters that had a kind of octopus look to them. All the Old Gods seem to have had cephalopod-like tentacles (though C'thun always kind of hybridized that with arthropod-like features,) but if we are to understand that the faceless and other such minions we dealt with in Cataclysm were mostly N'zoth's, it stands to reason that they take after their creator.
Ozumat looked like it might just be a huge octopus with too many eyes, but now I'm suspecting that it was, in fact, one of the top minions of N'Zoth.
While there are more blue tones in this image, the red eyes might have something to do with the red and black motif to the Emerald Nightmare.
But of course, even if the thing looks octopus-like, you also have the super-creepy implication that that thing in the middle opens up like a gaping maw where, were the thing an octopus, the bulk of its internal organs would be. Of course, we can be confident that what we're seeing is a tiny fraction of N'zoth's actual body, and I sure as hell don't know enough about the physiology of an Old God to even know if it has any central set of organs (more likely it just grows what it needs to support more body wherever it can.
We'll also be getting a better look at Y'Shaarj - currently our best representation is just the stained-glass window glimpsed in the temple beneath Klaxxi'vess, which really looks closer to a Faceless One (aka N'araqi.) I'd guess that Y'Shaarj probably looked more like the Sha, and I wonder whether the seven heads were literal.