This is my favorite billboard and it's everywhere; it says "We're working, are you?" with pictures of ants. And an old fashioned car.
This isn't really "propaganda" but it is a speech by Fidel, which is practically the same thing. This is written on the wall of the paladar I wrote about previously. At the top it says "For this we say, liberty or death!" Come on Fidel, lets be original.