In a large bowl, dissolve cherry gelatin and sugar in boiling cranberry juice. Add the ice cubes; stir until dissolved. Refrigerate until thickened, about 45 minutes.
Fold in the celery, pear, cranberries and 1/2 cup walnuts. Transfer to a 13-in. x 9-in. dish coated with cooking spray. Refrigerate until firm, about 50 minutes.
Meanwhile, in another bowl, dissolve lemon gelatin in water. Refrigerate until slightly thickened, about 35 minutes. Whisk in 1/4 cup mayonnaise; fold in the remaining mayonnaise. Fold in half of the whipped topping. Carefully spoon over cherry layer. Refrigerate until firm, about 45 minutes.
Spread with remaining whipped topping. Sprinkle with remaining walnuts. Refrigerate for at least 3 hours. Cut into squares.