I humbly wish to announce that, to a student of the Taote Ching, the yin-yang holds certain connotations and specific meaning, but in general isn't strictly associated with the unknown.
The association with the dragons also gives unintentional meaning insomuch as it implies, with the yin-yang, an umbrella over Eastern civilizations. Case in point- you wouldn't much expect to find Alexander or Catherine under this image, whatever the case.
I grant that it's pretty, and that the flame filter was used to the best possible effect, but using it to symbolize 'the unknown' is probably something akin to a freudian slip.
However, seeing this has forced me to consider what I would use to represent an improvement over the default image to symbolize the Earthly unknown, not just as an exploration of my own personal ignorance, but from a practical design standpoint as well.