I've been thinking about the contest for a while now. I had only vague ideas about possible character concepts and what element to choose. So I decided to think about the setting for the characters instead as a starting point.
I chose to interpret War of the Elements pretty literally. Four nations/alliances that are in a state of cold war. Border disputes, conflict over territory and resources as well as ideology are constant sources of friction. Alliances between the nations occur but these are unstable and short-lived in nature. All the nations have modern high-tech armies. Magic and element manipulation in particular is commonly used. Most militaries are composed of conventional armed forces + specialist magic wielding units. Tonally, I ended up thinking about the setting a bit like if it was for a miniature war game like Warhammer 40k or Infinity.
I wrote ideas about the nations in the form of bullet points that I could use while thumbnailing potential character concepts. The nations I thought about were the following.
Magma Union
A union of several city states united by trade and defense. Most of their territory is volcanic and mountainous, although they also have fertile plains. They focus on using magma manipulation and pyromancy. They also commonly use thermobaric and flame-based weaponry and their doctrine favours speed and aggression.
Whirpool Alliance
An alliance formed out of a multitude of islands and their settlements. There are some larger land masses, but their territory is mostly composed of small islands, reefs and atolls. The alliance consists of many disparate factions and groups that are united by many treaties and cooperation against external threats. Their navy is powerful, but their land forces are relatively small. The alliance utilizes both hydro- and cryokinesis. These are also utilized in more conventional weaponry. The alliance prefers evasion and taking full advantage of their mostly oceanic territory.
Granite Dominion
A militaristic unified state dominated by a struggle between isolationists and expansionists. Their territory is heavily mountainous, which means they have only limited farmland. They have a strong army and utilize ferro- and geokinesis as well as crystal manipulation to strengthen them even further. The Dominion prefers heavy armour and although they are not most mobile of armies they can use natural obstacles and chokepoints to great effect to mitigate this disadvantage in their home territory.
Volt Bloc
A recently formed aggressive unitary state. Currently acting highly belligerent towards their neighbors. Their territory is hot, humid and stormy and dominated by mountains, plateaus and lush jungle valleys. The Bloc uses electrokinesis and electromagnetism with their equipment focusing on supercharging these even more. Their conventional forces are relatively small but they wield a large variety of unconventional and irregular units.
Besides this I figured there would also be smaller polities, NGO's and other groups being used by the major nations or pursuing their own agendas. The major nations have only limited direct borders with each other.