This is an example of Perceptual forces and the use of asymmetrical balance. The picture is heavier on the bottom with most of the subjects body in that section of the frame, but her extended leg acts as a balancing line which draws the eye up ward. It is much more interesting than if both of her legs were up or both were down.
one of the neatest compression shoulder balances to experience- enter from Waterfall Pose, use your bellybutton as your drishti (aka your naval is your focal point) and settle/balance each joint compression. Seriously, with the pushing up and gravity letting your legs press down, this feels like floating!! Keep your spine stick straight please *shudder* spines are sorta important. And breathe :)