When I was a JW, they asked it this way: If your mother was killed by a gun, would you wear a little silver one around your neck to remember her by? Why would you want to celebrate or commemorate the exact manner of her death? And they had a point. Which is why JW's don't wear crosses or have them as decorations in the Kingdom Halls.
People who are against the death penalty are not going to wear little electric chairs around their necks, to remind people of the sacrifice made by the unjustly executed. Peaceniks don't wear jewelry made in the shape of bombs. Wearing a symbol--whether a flag, a peace sign or a swastika-- usually means you are in favor of it. It is not much of a stretch to think that Christians are promoting
crucifixion by wearing the device used to do the deed.
A hanging noose is still a hanging noose, and it would be damn medieval creepy to wear one as jewelry.
No matter how you try to pretty it up, sticking precious stones on it and whatnot.