This kind of sheet cake does not require decorating. It has a rustic, homemade feel to it. However, if you want to dress it up in the easiest way possible grab some fall sprinkles and adorn the top right after frosting it. Or for a slightly more elevated look create a grid pattern on the top of the cake where you want the slices to be. Do this carefully. Straight lines are essential. Place a candy pumpkin in the center of each square and lightly add fall colored jimmies or sprinkles. Viola! Pretty and delicious!