MIX 1-1/2 cups of the wafer crumbs, sugar and butter in 13x9-inch pan. Press firmly onto bottom of pan. Refrigerate until ready to use.
BEAT cream cheese in medium bowl until well blended. Gently stir in 1/2 of the whipped topping. Spread evenly over crust.
STIR boiling water into gelatin in medium bowl 2 minutes until completely dissolved. Add enough ice cubes to cold water to measure 1-1/2 cups. Add to gelatin, stirring until slightly thickened. Remove any unmelted ice. Spoon slightly thickened gelatin over cream cheese layer.
REFRIGERATE 3 hours or until firm.
SPREAD remaining whipped topping over gelatin just before serving. Sprinkle remaining 1/4 cup wafer crumbs over whipped topping. Decorate sandwich cookies with icings to make "tombstones." Stand tombstones on top of dessert with candies to resemble a graveyard. Cut into 15 squares. Store leftover dessert in refrigerator.