As far as I know none of the picture cards allows to show a picture from an URL given as a sensor.state or attribute.
There is a workaround to use a generic camera with the URL to make this work using a template.
The possibility to enter the template in a picture card would also be fine.
Examples:
image_path: {{ state_attr( 'media_player.denon', 'entity_picture') }}
image_path: sensor.heos_denon_info