Add a background to a JFrame

I want to add a background to my JFrame, but I can't get it done. I have searched on the internet to find to some tutorials on it. I am still a newbie and I want to learn these things. This is what I have so far.

package gui;

import java.awt.Desktop;

public class Gui extends JFrame {

    private static final long serialVersionUID = 1L;
    private JPanel contentPane;
    private JLabel BackgroundLabel;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Gui frame = new Gui();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public Gui() {
        setTitle("Exile Launcher");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 1000, 563);
        contentPane = new JPanel();
        contentPane.setBorder(null);
        setContentPane(contentPane);
        contentPane.setLayout(null);

        BufferedImage BackgroundImage = null;
        try {
            BackgroundImage = ImageIO.read(this.getClass().getResource("/Images/Background.jpg"));
        } catch (IOException ex) {
        }

        JLabel BackgroundLabel = new JLabel(new ImageIcon(BackgroundImage));

        add(BackgroundLabel);

        JButton HomeButton = new JButton("Home");
        HomeButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    Desktop.getDesktop().browse(new URL("http://www.google.nl").toURI());
                } catch (MalformedURLException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (URISyntaxException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
        });

        HomeButton.setBounds(10, 9, 50, 50);
        contentPane.add(HomeButton);

        JButton ForumButton = new JButton("Vote");
        ForumButton.setBounds(10, 70, 50, 50);
        contentPane.add(ForumButton);

        JButton VoteButton = new JButton("New button");
        VoteButton.setBounds(10, 131, 50, 50);
        contentPane.add(VoteButton);
    }
}

But I get this error:

java.lang.IllegalArgumentException: input == null!
    at javax.imageio.ImageIO.read(ImageIO.java:1388)
    at gui.Gui.<init>(Gui.java:59)
    at gui.Gui$1.run(Gui.java:36)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:312)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:694)
    at java.awt.EventQueue$3.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)