How can I get images to appear in UI PickerView Component in Swift?

I am trying to use images in a Swift PickerView. I don't know how to get the images to actually appear in the component. I know how to do this using Strings with the titleForRow function but I don't know how to do this using images. Here is my code so far:

import UIKitclass ViewController: UIViewController, UIPickerViewDelegate {    @IBOutlet weak var pickerView: UIPickerView!    var imageArray: [UIImage] = [UIImage(named: "washington.jpg")!,        UIImage(named: "berlin.jpg")!, UIImage(named: "beijing.jpg")!,        UIImage(named: "tokyo.jpg")!]    override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view, typically from a nib.    }    override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }    // returns the number of 'columns' to display.    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int{        return 1    }    // returns the # of rows in each component..    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {        return imageArray.count    }}// end of app