core/homeassistant/components/bluesound/icons.json

{
  "services": {
    "join": {
      "service": "mdi:link-variant"
    },
    "unjoin": {
      "service": "mdi:link-variant-off"
    },
    "set_sleep_timer": {
      "service": "mdi:sleep"
    },
    "clear_sleep_timer": {
      "service": "mdi:sleep-off"
    }
  }
}