The only reason a player can see your heads, bodies, shields, etc is because they are stored on their device. If they weren't stored on their device, the image wouldn't show up and you would have no head/body/etc on their screen.

I do agree that they should have a system that before they upload they can see if a similar head/body/etc has been uploaded. Maybe they do, I'm not sure.

But most heads/bodies/etc are just edits and recolors of an original set of heads/bodies/etc. So in reality, "original heads/bodies/etc" aren't that original at all unless you made from scratch. But if you did make from scratch, you gotta realize people are going to use your stuff sometimes.