This picture strikes me for its colors and its mood. It conveys such a sweet and tender, yet painful feeling that is visible through the imagery of butterflies and flowers that surround Derpy and the shadow cast over her by the tree. To me, that symbolizes Derpy's separation from the bright, happy and colorful land of Equestria and her immersion in the weirdness of being alone in the shadow. Another thing I love is the sky. The colors blend so well despite not being physically blended. The tree is striking as well, with the reddish brown mellowing out the brighter colors.