I like this picture by Henri Cartier-Bresson. This picture uses the simplicity of a black and white picture and is simple in general. The reflection of the kid in the water gives a really nice effect that attracts viewers to view this picture.
Street in Venice, John Singer Sargent, 1882 --This one hangs in the National Gallery of Art. Sargent did a huge string of Venice street paintings in watercolor and in oil--extremely energetic and vivid to me.