Custom markers with Flutter Google Maps plugin

Is there a way to display custom markers with the official Flutter Google Maps plugin on the map? Can't find any way to do it based on the documentation.

    BitmapDescriptor customIcon;

    // make sure to initialize before map loading
    BitmapDescriptor.fromAssetImage(ImageConfiguration(size: Size(12, 12)),
            'assets/images/car-icon.png')
        .then((d) {
      customIcon = d;
    });

    final nearbyCarsLocation = [
      LatLng(24.9286825, 67.0403249),
      LatLng(24.985577, 67.0661056), //24.9294892,67.0391903,18.73z
    ];

    void _getNearByCars() {

      for (var i = 0; i < nearbyCarsLocation.length; i++) {
        var now = new DateTime.now().millisecondsSinceEpoch;
        _markers.add(Marker(
          markerId: MarkerId(nearbyCarsLocation[i].toString() + now.toString()),
          position: nearbyCarsLocation[i],
          // infoWindow: InfoWindow(title: address, snippet: "go here"),
          icon: customIcon ));
      }
      notifyListeners();
    }

Hope this will help in getting custom nearby localities