Place potatoes in a large saucepan; add water to cover. Bring to a boil. Reduce heat; cook, uncovered, until tender, 15-20 minutes. Drain; cool completely., Cut potatoes into 3/4-in. cubes; place in a large bowl. Chop four eggs; slice remaining egg. Add chopped eggs, pickles and onion to potatoes. Mix mayonnaise, celery seed, salt and pepper; stir gently into potato mixture., Top with sliced egg and sprinkle with paprika. Refrigerate, covered, at least 2 hours before serving.