The skin used by the new tiger mount (under all its armour) is a regular Pandaren Tiger skin, but isn't quite the same colour as any existing one. It's obviously derived from the Frost skin, but is more yellowed and has tan claws. The pelt colour is similar to the "white" skin, but lighter:

As a comparison, here's the existing Frost and White (grey) ones:


The other is obviously the new Darkmoon wolf boss, "Moonfang". This one is a bit less novel in that he uses the standard white/light blue worg skin, just with glowing blue eyes which are pretty cool:

Sadly, neither of these skins exists in the relevant folder for its wild beast version, but hopefully they'll be copied across.
There's also a new "Kor'kron" wolf model that based on the Horde PvP wolf mount, but sadly they still haven't made a no-armour version of it. I was hopeful
