self.navigationBar.setBackgroundImage(UIImage(), for: .default)
self.navigationBar.shadowImage = UIImage()

let image = UIImage(named: "background")
let bgImageView = UIImageView(frame: CGRect(x: 0, y: 0, width: view.frame.width, height: view.frame.height))
bgImageView.image = image
self.view.insertSubview(bgImageView, at: 0)