Place one of the sheet cakes down first as the castle base and frost it. Again, your choice of flavor. I think a white frosting might be a good choice for a silvery castle and black would be a really dark, scary castle. Even orange could be fun.
Then, before placing the second sheet on top of that, cut off sections to leave some areas one level and others two levels. Save the extra pieces to build up a third layer. You are creating a multi-level castle. On the version above, about one-quarter of the cake was removed and then cut into three equal sections that became platforms for the turrets (those are the cone-shaped portions of the castle that help make a castle look castle-y.)
Ice the second layer. Add the third layers and frost.
Now comes the fun part of decorating. To make the turrets, cover some ice cream cones with icing and sprinkles. You could also use the square flat-bottomed cones for the square type of turret. If you have some of those cocktail flags, add them on top of the turrets. They are even available as country flags if you want to represent a particular place.
Next, add caramel squares to form the crenelations along the top of the castle. If you want to get particular, the openings are the crenels and the merlons are the square sawteeth. See how that architecture background just snuck in there? I know odd stuff like this. Glad to see those classes paying off. Okay, so you have your turrets and crenelations complete, so you should start recognizing your castle for what it is. But, it cannot be a castle without a drawbridge. No way. No how.
Use candy bar squares to make the bridge and the castle door. Then use small pretzel sticks as the drawbridge chains. The rest of the decorations are up to you. I have found in the past that the dollar stores usually have some decorations to add to the top that can double as prizes. The pumpkin, witch, and Frankenstein are something I found one year. M&M's surround the base, and large chocolate eyes became drawbridge decorations. Not everything needs to be historically accurate. Monsters on the castle should definitely be historically accurate, though.
The rest was decorated in a similar fashion to the first, switching the design only slightly. On both I added side windows using candy bar squares sprinkled with yellow sprinkles. A real castle would not have windows like that. They should really be arched but that was getting a wee bit complicated, even for me.
So there you have it! Two haunted castle designs for a Halloween party kids will remember for a long time. Did I mention it tastes delicious?