core/homeassistant/components/event/icons.json

{
  "entity_component": {
    "_": {
      "default": "mdi:eye-check"
    },
    "button": {
      "default": "mdi:gesture-tap-button"
    },
    "doorbell": {
      "default": "mdi:doorbell"
    },
    "motion": {
      "default": "mdi:motion-sensor"
    }
  }
}