Using a picture as background to the card

[Lupi00]

I love this card because of the way it look and how fast it is compared to other cards with the same features.

My question is if it is possible to get a picture as a background on these cards?
I use a grid on my dashboard which makes the buttons quite large so that I can use a ipad as a control device. This means how ever that a lot of the space in the card is, well nothing. If I can specify a picture as background it would make the button a lot better looking.

Is this doable and if so, what do I need to add to the code?

Thank you!

My button looks like this.

And the code is

type: custom:slider-button-card
entity: light.fonsterbelysning_kok
slider:
direction: left-right
background: gradient
use_state_color: true
use_percentage_bg_opacity: false
show_track: false
toggle_on_click: false
force_square: true
show_attribute: false
show_name: true
show_state: true
compact: false
icon:
show: true
use_state_color: true
tap_action:
action: more-info
icon: mdi:ceiling-light-multiple
action_button:
mode: toggle
icon: mdi:power
show: true
show_spinner: true
tap_action:
action: toggle
name: Fönster
attribute: friendly_name