Wearing a Buddha Icon is a more or less irrelevant. The fact that people do wear such jewelry really does not mean anything. It is in fact probably just an expression of ignorance. The Buddha did not ask us to wear jewelry with his image on it. In stead he asked us to do something about our overwhelming immersion in illusion. At most it signifies nothing, which if that reminds us of emptiness is probably good but not good enough to actually signify anything, without personal action on the path of the bodhisattva.