When I think of that I think of people in a house surrounded by zombies. So, maybe, a round cake with people gathered around watching tv (top) and around the cake (around on the side of the cake) zombies circling them?
You could do a dome cake like a little Earth and carve in some big cracks, you could pipe in runny orange coloured white chocolate or royal icing as lava bubbling out.... .....I want an end of the world order now!!! lol