My Alternate Ending Idea...
After Sergeant Howie is burned to death in the wicker man, the scene should've flashed to an update of a failed harvest. All the citizens would blame Lord Summerisle for the failure of the harvest. All the plant life begins dying. Lord Summerisle begins freaking out, realizing that his religious beliefs were false, and that his people no longer trust him. The sky becomes dark, the clouds become blackened, thunder begins rumbling throughout the island, and in the distance Lord Summerisle hears the haunting sounds of Sergeant Howie saying "A CUUUURRRRRSSSSSEEEE!!!!!!"
Even though this movie is a definite "cult" classic, and the ending is unforgettable...I still think that would've made a cool alternate ending.