open fields are perfectly fine they just need detail in them to be more pleasing to the eye, if you find you want to stay truer to the original location simply try putting in bushes, trees, craters, rocks, ammo crates, burnt out vehicle wrecks and other such things that don't take away from the original location but add to the atmosphere of things that may have been there at the time of battle, things left behind by the population as they ran from the fighting, or things brought to the area by the armies, such as supplies and vehicles.