I have always liked paintings where an idea, concept is conveyed. The good example of this would be http://www.themasterpiececards.com/...itian's Allegory of Prudence-resized-600.JPG". But I have always failed to appreciate any beauty or anything good at all about paintings like Mona Lisa by Leonardo da Vinci or Black Square by Kazimir Malevich. What is so good about them? Could you please guide me?