Volumio Add the picture_entity as a background image of a Button via attributes

Hello,

I have the below button and i’m trying to add from the volumio player the entity_picture api as a background image to button.
I have create a sensor with the picture entity path but doesn work.

      - type: custom:button-card
        entity: switch.out1in1s
        name: '[[[ return states["sensor.volumio_source"].state; ]]]'
        show_state: false
        color: blue
        icon: mdi:music-circle-outline
        styles:
          icon:
            - color: gray
            - width: 30px
            - margin-top: 0px
            - margin-left: 0px
          card:
            - height: 70px
            - width: 70px
            - transition: all 2s ease
            - background-image: url'[[[ return states["sensor.volumio_picture"].state; ]]]'
        state:
          - value: 'on'
            styles:
              icon:
                - color: blue
              card:
                - '-webkit-box-shadow': 0 0 0.95rem 0.2rem blue
                - box-shadow: 0 0 0.95rem 0.2rem blue

# Configuration.yaml 

sensor:
  - platform: template
    sensors:
      volumio_picture:
        friendly_name: "Volumio Picture"
        value_template: "{{ state_attr('media_player.volumio', 'entity_picture') }}"    

The result of the sensor is " /api/media_player_proxy/media_player.volumio?token=bb274580427051802debd2b2dbeb39ed281da8ce21dcf40296521a39c7aea7a0&cache=0107c404cf8d15bd "

Anyone for this?