Do you believe that the print on a graphic T-shirt carries information? Or, say, smiling? Because that's what we're dealing with here: a set of generally understood markers that you can wear or signify through your behavior or its context. Just because you don't see or, presumably, participate in it doesn't mean that it can't be a viable channel for others.

I'm not especially keen on taking you up on your earlier offer, because it would be too easy to select unrepresentative photos. But imagine that some third party dug up... oh, let's say a hundred photos like these, of men of similar age and ethnicity. I'll bet at almost any odds that observers with typical neurology and relevant cultural experience could look at those photos and use them to gauge the subjects' social class, place of residence, musical taste, hobbies, and dozens of other things at rates better than chance. Much better, if they're good at it.