Well, the throne only has three legs, and the guy holding the guillotine is making up for the missing leg by supporting the throne. He also has the string to the guillotine, so it could signify that everyone has the power to support or throw out the person in charge. However, because the guillotine is not in a position to behead someone, maybe it's showing that the people supporting the person in charge only believes they have the power to overthrow them, when in reality they don't. BUT because there is no one sitting in the throne, it may show that anyone willing to take that position of power is throwing themselves on the mercy of the people to either support them, or kill them. There are a lot of different interpretations, and anyone who has another idea, I would very much like to hear it.
*inhales deeply* Allow me. I believe that what it is trying to say is that when you start drinking alcohol you will get "hooked" on it, and fish who get hooked by a fisherman have a very bad time, to say the least. Not only that, but there is a flotation device staying at the level of the beer, which shows that the more you drink, the closer you get to being hooked by it. I guess you could say it's an elaborate anti-drinking picture. Again, anyone who has a different view, let me know.
The Washington, D.C. one is funny though