Ambras, specialist in gold earrings and assorted colored stone and gold jewelry, is now exclusive supplier of 10k and 14k gold Looney Tunes jewelry. It offers cast, electroformed and photoetched pieces featuring such characters as Bugs Bunny, Tweety Bird, Sylvester, Marvin the Martian and the Tasmanian Devil. Ambras Fine Jewelry Corp., 48 W. 37 St., New York, NY 10018; (212) 594-5252, fax (212) 268-1546.Asialuxe, a three-year-old, Hong Kong-based firm, signed an exclusive license agreement to manufacture and distribute a line of 18k gold and South Sea pearl jewelry under the Nina Ricci brand name worldwide (except in the Japanese domestic market). The line was launched at the October Tax Free World Exhibition in France at suggested duty-free retail prices of $350-$1,500. Asialuxe PS Ltd., 1401 Lyndhurst Tower, 1 Lyndhurst Terrace, Central, Hong Kong; (852) 2526-0251, fax (852) 2536-4210,