Can Someone help i am trying to get this to work to setup dynamic background for dashboard

Configuration Frontend
1 
type or paste code here
```input_text:
  background_image_url:
    name: Background Image URL
    initial: /local/saved_pictures/my.jpg
    max: 255
    background: >
      [[[ 
        var imageUrl = states['input_text.background_image_url'].state;
           return 'center / cover no-repeat fixed url(' + imageUrl + ')';
        
      ]]]
    background-size: cover;