Alright, playing into the druids and barbarians versus more formally educated society, what about massive cities connected by magical skyways, I'm picturing massive monorails that are powered by working-class mages which drive them similar to coal-powered trains. These cities are centers of technology (in the eberron sense of technology), but drain the natural resources of the world they're built upon and, because they're held high in the air by platforms and whatnot, blot out the sunlight.
Below them we put an extremely verdant natural world. This should be incredibly jungle-like and dense with enormous and voracious fauna and even flora which tries, by its nature, to destroy the civilization and reclaim the sky.
Both sides should be home to large societies which are powerfully devoted to their homes. More natural classes, druid, barbarian, etc should favor nature of course, but there could even be some crossover. Perhaps one tribe of druids has moved into the skycities and they are working to meld nature with the cities by producing floating gardens, while a group of wizards have moved into an ancient center of study that lay in ruins in the deep jungle and now fight off the civilization that nearly destroyed such ancient knowledge merely for the sake of progress.
This would give each side a powerfully vested interest in seeing their cause championed because it's their own home they're fighting for while at the same time allowing reasons for any individual class to exist on either side. Commoners may cling to the cities for protection, or they might live in harmony with nature after the traditions of their ancestors and defy the cities. Neither side should have enough of a regimented government to fully oppress the other.
Finally, I would put some form of mcguffin that prevents any group from attempting to outright devastate their opposition through force. Perhaps destroying the cities would result in some horrible fallout for the world's ecosystem and the cities cannot sustain themselves without the verdant energy of the natural world that they draw upon for power.
Anyway, its an idea. ^_^