You can use any cheese ball recipe that you like. Once mixed thoroughly, place in plastic wrap, like Handi Wrap. Then shape into a skull or use a mask and press into that. Chill thoroughly before serving. You might have to chill for a bit before you can shape it. Use sliced almonds for teeth and stuffed olives for eye balls. I kinda think I'd take the olives later for a dirty Martini! :)
With a mixer, blend 16 ounces room-temperature cream cheese with 1 1/2 cups shredded cheddar, 3 tablespoons minced onion, 2 tablespoons salsa, 2 teaspoons ground cumin and 1 teaspoon minced jalapeno. Scoop onto plastic wrap and use the wrap to form the mixture into a 5-inch pumpkin-shaped ball; chill at least 2 hours. To serve, unwrap, roll in crushed nacho-flavored tortilla chips or your choice of flavor, and press a bell pepper stem into the top.