Eloise, who made her debut in a rampantly popular book describing her capers in New York's stately Plaza Hotel (Life, Dec. 12, 1955), has had two important things happen to her recently. For one, she has been to France and in a new book, Eloise in Paris (Simon & Schuster, $3.50), she discusses her encounters with French traffic, pigeons and language. For another, she has become a figure in fashion. An Eloise wardrobe has just been created, available in sizes to fit all of her young admirers. They will also fit a life-sized doll, made in the image of Eloise, who wears size 6X clothes. There is a smaller doll, too, for miniature clothes. As a part of the Eloise boom, a new Eloise record. Eloise French postcards (fit for children) and a series of Eloise bonnets designed by Mr. John will soon appear - and an Eloise radio show with Eloise starring as disc jockey is being set up. "The Eloise boom," says her creator, Kay Thompson, "is not likely to make little girls more remarkably fiendish then they already are. That isn't possible."