The whole soda fountain phenomenon was before our time, so I'm not sure that milkshakes were available at most soda fountains, but it's easy to imagine the tableau relocated to the ice cream shop. The "milkshake icon" seems more evocative than the "soda icon".
http://www.best-norman-rockwell-art.com/images/1921-Norman-R...
The whole soda fountain phenomenon was before our time, so I'm not sure that milkshakes were available at most soda fountains, but it's easy to imagine the tableau relocated to the ice cream shop. The "milkshake icon" seems more evocative than the "soda icon".