Finland, during the Winter War (or whatever it's called in English). War against the Soviets, during WW2.
The 30-years war. Basically Sweden harrying the Holy Roman Empire, with some French and English (Scots) thrown in.
Warhammer 40.000, or similar (less copyrighted) arena.
A manga/anime map. Say, Neon Genesis style, fighting for Tokyo against the Apostles. Or something similar. Bound to be a hit, and prolly a croud pleaser with the younger crowd.
WW3, based on modern analyses. Nuclear war starting in the Middle-East, Korea, India/Pakistan or wherever strikes your fancy. With the US and perhaps Russia as major players, ofc. Tom Clancy style.
WWZ. The zombie wars. Something true to the genre.
Dune. Warring over spice.
Prohibition and 30's gangster warfare.
Cthulhu cultists overrunning New England, and perhaps even the Athlantic.
Just a few random ideas. If you've already been thinking along any of these lines, go ahead with it! If not, maybe you'd be interested in realizing something similar? In any casy, I'd play any or all of these.