BOSTON-- Arnold last week began to roll out its latest image ads for Volkswagen of America.The effort includes a 30-second TV commercial, "Really on Doug's Mind," showing a man at home, work and walking through the street as a VW Beetle attached to his head grows steadily larger, much to the chagrin of onlookers, family and friends. Ultimately, the car is enormous and Doug is urged by everone to "buy it!" rather than let it grow on him in such a fashion. The client's familiar "Drivers wanted" tagline, introduced by the Boston agency when it won the business six years ago, is retained. That spot is one of three new humorous commercials designed to support the brand in general while -- unlike other recent ads for the client -- not stressing specific models or features.Volkswagen of America is Arnold's largest single account, spending $350 million on ads in 2000 and $270 million through Sept. 2001, according to CMR.