Striking and enigmatic image, with an unassuming presentation. I feel like there is a person to know in this portrait. Nice take on the challenge theme.
Whilst I like the concept and the image itself I am not sure about the muted and somewhat cold greeney-blue colour tones. The skin looks unaturally coloured such that it gives an air of poor health to the model which I doubt is the reality.
While that pose certainly shows balance, I get more of a sense of stress/tension than I do of relaxed peacefulness; I suppose I'm imagining what I would feel like if I attempted to assume that position. Coloring, lighting, background and crop all work well.
Unusual shot, washed out look and relaxed crop gives it an ethereal feel. Perhaps a little more light under the legs would soften the slight harshness of the shadow here, if you want to reveal more of what she is balanced on. Not sure how "peace"ful it is but certainly out of the norm.
II like the concept and colors just wish she was separated from the back wall more. Some sort of subtle side or back light to help give her 3 dimensions would have helped I think.
I understand what you are trying to say here but my own experience gets in the way. When I try to balance, I feel under pressure not to do anything that would upset the balance. I suppose that if you practice yoga long enough, you can get a sense of peace from a balance posture.