just use something like WW2: Protection of the Free World, or WW2: Total War, Freedom vs. Facism, etc. There are many things you could use. And they don't have to be historically accurate really, because if it's a good mod no one will really care about the title. It would also depend on the setting of this mod too. WW2: Battle of the Atlantic, Liberation of Western Europe, The Pacific Theater, etc.
Or just use Allies and Axis