So, it seems Rebels and Revolutionaries won the poll for the January theme. Some suggestions:
Great War - Irish Republican Army.
World Ablaze (which I'm taking to include interwar) Spanish Civil War. Republicans, Nationalists, Anarchists, Communists. Almost all of which might find use in WW2 proper. MORE REALLY SMALL TANKS!!!
Imperial Conquests - Italian War of Independance! Garibaldi
Napoleon's Wars - Spanish Guerillas. Maybe wind the clock back a bit and cover the French Revolution too?
Renaissance - take your pick of the Wars of Religion, but if this line is now taking in Medieval than you could do no better than Robin Hood. Thought that might be a good pick for Classic Fantasy, really...
Death Fields - Cyberpunk renegades. You know you want to go there.