core/homeassistant/components/timer/icons.json

{
  "services": {
    "start": {
      "service": "mdi:play"
    },
    "pause": {
      "service": "mdi:pause"
    },
    "cancel": {
      "service": "mdi:cancel"
    },
    "finish": {
      "service": "mdi:check"
    },
    "change": {
      "service": "mdi:pencil"
    },
    "reload": {
      "service": "mdi:reload"
    }
  }
}