Mix powdered sugar and cracker crumbs in medium bowl. Heat butter and peanut butter in 1-quart saucepan over low heat, stirring occasionally, until melted. Stir into crumb mixture. Press in ungreased square pan, 8x8x2 inches.
Heat chocolate chips in 1-quart saucepan over low heat, stirring frequently, until melted. Spread over crumb mixture. Immediately sprinkle with candy decorations. Refrigerate about 30 minutes or until firm. Cut into 6 rows by 6 rows. (To cut diamond shapes, first cut straight parallel lines 1 to 1 1/2 inches apart down the length of the pan. Second, cut diagonal lines 1 to 1 1/2 inches apart across the straight cuts.) Store loosely covered in refrigerator.