Transparent issues?

I had an idea to make a player skin of a skull, leaving the rest of the body transparent so that the player would look like they were just a floating skull, no hands or legs or body. However, when I uploaded it to see how it looked in game, all the transparent parts had turned a solid black. Does anyone know how I might fix this, or what i did wrong?

I’ll include some images too so you can see what I’m talking about

Mojang does not allow transparency on the skins