Carnival Atmosphere   If ever there was fun in fund raising it was on the afternoon of Sept. 19, when the Washington Market Park held its first carnival. Tickets could be purchased for everything from crafts to cotton candy, with the money going to support the park’s popular arts program. (The free program is held in the park every Monday and Wednesday, from 3 to 5 p.m., and every other Saturday from 10 a.m. to 3 p.m. through October.) “It really brought a lot of people together,” said Liz Liebeskind, who helped organize the festivities for the park’s board of directors. “I get that kind of carnival feeling when I go upstate and that’s what I wanted to bring down here.” Though the carnival is over, it’s not too late to contribute toward the $20,000 a year the program costs, says Liebeskind. Donations earmarked for the program can be sent to Washington Market Community Park, Inc., 295 Greenwich St., Box 227, N.Y., N.Y., 10007.