(Pics) Halo 3 Armor Permutations

Here is an awesome pics of Halo 3 Armor Permutations - characters are

Spartan Permutations
Mark VI, Mark V, CQB, EVA, EOB, Rogue (Regulator), ODST, Scout, Hayabusa (Samurai), Security (Marathon), Unknown 1

Elite Permutations
Combat, Assault, Flight Mark, Commando, Ascetic

Check them out! My absolute favorite is Samurai.
Question is, are all of these available models to players or are they non-player models? And how could I unlock these? By finding the skulls?

I guess what all of these are unlocked by Achievements and beating certain levels in the game on different difficulties. Also, some could be unlocked by the skulls. You unlock different pieces as you go too, you don't unlock the full set (Body, Helmet, Shoulders) All at the same time.