One of the qualities of a good photo is a nice combination of light, shade, figure and form. A good photo, especially a good erotic photo, should evoke something, a type of atmosphere, a more ethereal quality which helps us escape from the mundane sameness of our daily material world. Healthy love and eroticism must always be imbued with a certain degree of spirituality, or at least psychology. Sex cannot be merely physical; it must also be spiritual, rooted in some type of love, and seeking some type of transcendence.
Art has the power to express these things, whether in writing or painting or photography. Photography is a great modern medium for erotic art, because it is both real, yet also imaginary. A good nude photo can represent and ideal of love and beauty, of the mysteries of sensuality and eroticism, in a way that few other artistic mediums can.
I find the above photo a nice example of such things. There is nothing too extravagant in this photo, and yet in its simplicity, a nude set against a soft white background, there is a sense of mystery and beauty that somehow expresses something deeper than the mere physicality of a nude body. It is a nude which hints at the fuller meanings of our erotic existence, the love and beauties of life, and the healthy respect for the hidden yet ever present powers of our sexuality.