One memorable way to advertise, use an eye catching car to be a mobile billboard, like this Messerschmitt

Cool photos from Reservatory6.blogspot of interesting and unusual vehicles

 I've never seen a Jeep like this before

 One cabriolet and one hardtop Messerschmitt. A good gallery of Messers can be seen at http://pour15minutesdamour.blogspot.com/2009/10/transports-messerschmitt-kr-200.html which shows several levels of options, both on the dash, and on the exterior

 Belfast, Northern Ireland, 1944. Notice the gas tank (coal gas)

Found among many interesting cool vehicles on http://reservatory6.blogspot.com/