Code

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.sql.Date;
import java.util.Calendar;




















import java.util.logging.Level;
import java.util.logging.Logger;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.border.EmptyBorder;





public class main extends JFrame {


    private JPanel contentPane;
    public JLabel background;
    public JLabel background2;
    private Timer timer;
    private Timer timer2;
    private int counter = 2;
    private int counter2 = 2;
    private BufferedImage img;

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

    /**
     * Create the frame.
     * @throws IOException
     */

    @SuppressWarnings("deprecation")
    public main() throws IOException {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));

        final JLabel background = new JLabel(new ImageIcon("C:/Documents and Settings/All Users/Dokumenty/Moje obrazy/Przykładowe obrazy/Zima.jpg"));
        final JLabel background2 = new JLabel(new ImageIcon("C:/Documents and Settings/All Users/Dokumenty/Moje obrazy/Przykładowe obrazy/fds.jpg"));



        contentPane.addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent arg0) {
                System.exit(0);
            }
        });


        final ActionListener action2 = new ActionListener()
        {
            public void actionPerformed(ActionEvent event)
            {
                if(counter2 == 0)
                {
                    remove(background2);
                    contentPane.repaint();
                }
                else
                {
                    counter2--;
                    System.out.printf("%d", counter2);
                }
            }
        };



         ActionListener action = new ActionListener()
            {
                @Override
                public void actionPerformed(ActionEvent event)
                {
                   if(counter == 0)
                   {
                       remove(background);
                       contentPane.repaint();

                       getContentPane().add(background2);
                       revalidate();
                       timer2 = new Timer(1000, action2);
                       timer2.setInitialDelay(0);
                       timer2.start();

                   }
                   else
                   {
                       counter--;
                   }
                }
            };






        setUndecorated(true);
        setContentPane(contentPane);
        setTitle("Game");
        GraphicsEnvironment graphicsEnvironment=GraphicsEnvironment.getLocalGraphicsEnvironment();
        Rectangle maximumWindowBounds=graphicsEnvironment.getMaximumWindowBounds();
        setBounds(maximumWindowBounds);
        background.setBounds(maximumWindowBounds);
        background.setSize( maximumWindowBounds.width, maximumWindowBounds.height);
        timer = new Timer(1000, action);
        timer.setInitialDelay(0);
        timer.start();
        getContentPane().add(background);
        revalidate();
        repaint();
    }



}