Yes you can do it like this:
type: custom:mushroom-template-card
icon: ''
primary: LS50
secondary: '{{ states(entity) | title }} '
entity: switch.lounge_amp_center
fill_container: false
multiline_secondary: false
picture: /local/ls50.png
card_mod:
style: |
mushroom-card {
{{ 'filter: grayscale(100%);' if is_state('switch.lounge_amp_center', 'off') }}
}