agregar iconos al mapa en mapbox

gistfile1.js

function mostrarMapa(){

	var geoJson = [];
	var map = L.mapbox.map('mapbox', 'osgux.g99506jm');

	$.getJSON('js/estaciones.json', function(response){		
		$.each(response, function(index, item){			
			geoJson.push({
			    "type": "Feature",
			    "geometry": {
			        "type": "Point",
			        "coordinates": [item.longitud,item.latitud]
			    },
			    "properties": {
			        "title": "Estación " + item.estacion,
			        "icon": {
			            "iconUrl": "./js/train.png",
			            "iconSize": [32, 37]
			        }
			    }
			});
			
			map.markerLayer.on('layeradd', function(e) {
			    var marker = e.layer,
			        feature = marker.feature;

			    marker.setIcon(L.icon(feature.properties.icon));
			});	
			map.markerLayer.setGeoJSON(geoJson);							 
		});				
	});		
}