Heat water and sugar to boiling in 2-quart saucepan, stirring occasionally; boil 1 minute. Stir in cranberries. Heat to boiling; boil 5 minutes, stirring occasionally. Stir in gelatin until dissolved. Stir in pineapple, celery and walnuts.
Pour into ungreased 6-cup mold, 8 individual molds or stemmed goblets. Cover and refrigerate at least 6 hours until firm. Unmold onto salad greens. Garnish with celery leaves and additional cranberries, if desired.