I guess chocolate would be the visual thing there. I can tell you that here, in the french speaking part of Switzerland (and also in France), the belgians have a stereotype of being stupid and are generally used as the "dumb nationality" in jokes. Thats all i can really say. I know some belgian people so I'll ask them if I see them if they can think of a national symbol. I can also confirm that their beer is bloody good! Leffe forever!