The Mona Lisa has many principals of art found within it. One is contrast. As you look at the painting, colors in the background are much lighter in tone than the foreground. The foreground uses darker colors, giving a more serious feel to the subject matter. Another principle found in the Mona Lisa

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artists need to create a realistic interpretation so that people in general can relate to the artwork. for a common people, an artist's impression gets increased only if he can create something which would look realistic. an abstract is difficult for a common people to understand whereas if a person can draw a girl with simple pencil sketch and if that looks like a real figure then the latter will be praised more than the former.