I've got three for you....
The first is simple: Look at the old 1st edition PHB and Hackmaster PHB covers. See the scene where the adventurers are clustered around and on the statue (?) of the demon desperately fighting off monsters? I was looking at that cover in the store the other day and inspired to create an adventure that would include that scene. Music to go along with it would be good.
The second: The camera pans across a huge and ancient city, the capital of an empire. Fade to a scene showing victorious imperial soldiers parade through the streets of the capital in triumph with all of the spoils of victory among and behind them as crowds of citizens cheer. The Emperor, a tall and handsome man, leads the procession as members of the Senate look gravely on. Soon, the troops are dismissed and the city is filled with celebration of every kind.
The third: A dark and overcast day made even darker by the smoke rising from the ruined fortress in the background. A mighty fortress in a rugged mountain pass, it was meant to keep the monsterous barbarians, both nomadic and not, on the other side of the pass and protect the empire for eternity. Now it is fallen and in ruin. With it, the Empire is in great danger. The ground is covered with the corpses of dead imperial soldiers and barbarians alike, but the barbarians own the field. They loot and pillage, but there is an edge to their triumph. They search not just for wealth, but food and supplies. Even as they celebrate, the barbarians look back the way they came as if driven by something even more terrible than they....