Boards
How unusual would an item in your bin need to be in order for you to notice in when using your bin normally?
Like, don't think I'd ever notice if there was a human hand in my bin. Don't think I pay enough attention to it. But a head, yeah reckon I'd notice that.
Don't feel you have to be limited to a body part. You might for example be astute enough to notice a different brand of yoghurt pot from your usual brand. Or perhaps there could be a steering lock in there and you wouldn't notice. Just go for it.