var skyBoxGeometry = new THREE.BoxGeometry( 5000, 5000, 5000 );

var texture = new THREE.TextureLoader().load("images/sky.jpg");

var skyBoxMaterial = new THREE.MeshBasicMaterial( { map:texture, side: THREE.DoubleSide } );

var skyBox = new THREE.Mesh( skyBoxGeometry, skyBoxMaterial );

scene.add(skyBox);