Here is a java swing code that displays background image.

import java.awt.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.swing.*;

public class BackgroundImage{
private BufferedImage image;
private JPanel panel = new JPanel(new GridLayout(4,2)) {
protected void paintComponent(Graphics g){
super.paintComponent(g);
if (image != null){
g.drawImage(image, 0, 0, this);
}
}
};
public BackgroundImage(){
try{
File file=new File("C:\\rose.jpg");
image = ImageIO.read(file);
Dimension imageSize = new Dimension(image.getWidth(), image.getHeight());
panel.setPreferredSize(imageSize);
JLabel label1=new JLabel("Username: ");
JLabel label2=new JLabel("Password: ");
JTextField text1=new JTextField(10);
JTextField text2=new JTextField(10);
JButton b1=new JButton("Login");
panel.add(label1);
panel.add(text1);
panel.add(label2);
panel.add(text2);
panel.add(b1);
}
catch (Exception e){}
}
public JPanel getPanel(){
return panel;
}
public static void main(String[] args) {
JFrame frame = new JFrame("BackgroundImage ");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new BackgroundImage().getPanel());
frame.setSize(300,150);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}

You can also visit the following link:

http://www.roseindia.net/tutorial/java/swing/transparentImage.html

thanks sir