NetherRealm Studiios has admitted that Killer Frost and Ares are part of the Injustice: Gods Among Us roster.
As the above trailer shows, Killer Frost predictably has more than a little in common with Sub-Zero, what with the ice powers and everything, though her abilities widely seem far more interesting than ol’ Subs’. In fact, Killer Frost does the sorts of things it always seemed like Sub-Zero should have been doing, what with the icicle impalement and the freezing touch and whatnot. Meanwhile, Ares sounds like Dark Helmet from Spaceballs and has the ability to summon a multitude of different weapons, as one might expect from the god of war.
In related news, NetherRealm Studios also unveiled an alternate Batman costume based on Batman Beyond, which can be seen below.