Just add your if/on to the --icon-animation like this:
type: custom:vertical-stack-in-card
mode: vertical
fill_container: true
cards:
- type: custom:vertical-stack-in-card
horizontal: true
cards:
- type: custom:mushroom-template-card
entity: switch.cctv
layout: vertical
icon: |-
{% if is_state(entity, 'on') %}
mdi:cctv
{% else %}
mdi:cctv-off
{% endif %}
icon_color: |-
{% if is_state(entity, 'on') %}
yellow
{% else %}
#6f6f6f
{% endif %}
card_mod:
style:
mushroom-shape-icon$: |
ha-icon {
{% if is_state(config.entity, 'on') %}
--icon-animation: scan 5s ease-in-out infinite;
{% endif %}
transform-origin: 90% 80%
}
@keyframes scan {
0%, 100% { transform: rotate(20deg); }
50% { transform: rotate(-15deg); }
}