/**
 * <br>Created on 2010-11-11
 * @author Alex.Huang
 */
package ext.test.jws.gui;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

/**
 * <br>Created on 2010-11-11
 * @author Alex.Huang
 */
public class PanelImageTest extends JPanel {
   private Image image;

   public PanelImageTest() {
      super();
      setOpaque(true);

      image = Toolkit.getDefaultToolkit().getImage( "D:/My Document/My Pictures/Wallpaper Images/NOAA/line0053.jpg"); ;
   }

   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      setBackground(Color.WHITE);
      if (image != null) {
         int height = image.getHeight(this);
         int width = image.getWidth(this);

         if (height != -1 && height > getHeight())
            height = getHeight();

         if (width != -1 && width > getWidth())
            width = getWidth();

         int x = (int) (((double) (getWidth() - width)) / 2.0);
         int y = (int) (((double) (getHeight() - height)) / 2.0);
         g.drawImage(image, x, y, width, height, this);
      }
   }
   
   public static void main(String[] args) {
      JFrame frame=new JFrame();
      PanelImageTest panel=new PanelImageTest();
      JButton b=new JButton("按钮");
      panel.add(b);
      frame.add(panel);
      frame.setVisible(true);
   }

}

------解决方案--------------------
Java code

import java.awt.Graphics;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Background extends JFrame{
    ImageIcon image;
    JLabel imageLabel;
    JPanel backgroundPane;
    public Background() {
        image = new ImageIcon(Background.class.getClassLoader().getResource("images/background.gif"));
        backgroundPane = new JPanel();
        imageLabel = new JLabel(image);
        backgroundPane.add(imageLabel);
        this.add(backgroundPane);
        this.setBounds(200, 300, 381, 330);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    public void paint(Graphics g) {
        g.drawImage(image.getImage(), 0, 20, this);
    }
    
    public static void main(String[] args) {
        Background bg = new Background();
    }
    
}