I've been told that Ho Chi Mihn's face is somewhere on those tanks; apparently some Boston Gas employee painted Uncle Ho, just to stick it to The Man. From Boston Online: (link now dead)

Uncle Ho figures more prominently in the history of the Boston Gas tank in Dorchester. The tank is covered in a giant rainbow design (the largest copyrighted piece of work in the country) by artist Corita Kent. As you drive by, look at the left side of the blue stripe. A face begins to emerge. It's Ho Chi Minh! Boston Gas claims it's a coincidence; some suspect Kent, an anti-war activist, included Ho as a subtle protest (Kent herself isn't talking; she's dead).

So are Ho's victims, but Kent probably got a nicer send-off.