The Minneapolis Institute of Art got a little more publicity than it bargained for when it paid for billboards advertising its Titian exhibit. The signs featured the bare-breasted goddess from Titian's 16th-century painting Venus Rising from the Sea. But a graffiti artist with a sense of humor was apparently concerned about too much exposure in the dead of winter. On a billboard in Long Lake the vandal spray-painted a red strapless bra over Venus's bare breasts, and added a special touch in the form of an accompanying phrase: "Brrr!" Not quite a Titian, but we call it art.