Well one is ice instead of water with some death and demon stuff thrown in, while the other is just the cliche fire but with the addition of some warloks using black magic. The key, in my eyes, is to take a unique twist on something common or to just do a sort of mix.

Unless requested I won't create all the nations, because i certainly can't RP as all of them. But just incase BBeast or someone is inneed of inspiration, I'll throw a few ideas out there.

Astrology with constellations and star worship, maybe priest with power to transform into their Zodiacs

Oneiromancy (dream magic) perhaps with ancestor worship or something. This is strange and might sound weak, but think of powerful a caste of sorcerers could be if they could speak to ther ancestors for advice, and manipulate the dreams of those around them to subconsciously manipulate them, pose as gods, etc.

Golemancy, with a nation that creates magic creatures to fight or perform menial labor. 

Dust/sand, with a desert-dwelling tribe able to summon sandstorms to wear down and split up invaders. They could also utilize ambush tactics, appearig out of the dunes themselves to attack an amy's flanks, only to dissipate into clouds of dust the instant the battle begins to turn its favor.

Bestialism. The ability to control/speak with animals, an possibly transform into them.

Plague/Disease. Like the magic of Balon or Lugubrious' Blighted Men.

Anybody can feel free to expand on any or none of these ideas, and take or reject any of the three previous and more refined nations.