I'm not an atheist. But I am also decidedly not a Christian. Just a spiritual person in my own way. And: I would never wear a cross just as a "fashion statement"! Because I respect the power of symbols, and what they really represent! It would feel very, very wrong for me, wearing a symbol of something I completely reject, and that does not in any way represent me!
Only scenario in which I might consider making an exception..? Is if I dearly loved someone who died, and they left me that cross. In that case, I might consider wearing it as a physical symbol of my connection to them! Kind of in the same way as I wear the rings my grandma left me, every day, although they're not really my style.. It is my tangible, physical link to HER! That's all. :)