Try this plain vanilla simplest one on your environment after you
download it:
http://homepage1.nifty.com/algafield/BgImg.jar

If it does work on your machine, the cause of the problem might be some
config
issue for your development environment we can't make stabs in the dark
about it.

[souce code]
import javax.swing.*;
import java.awt.*;
import javax.swing.table.*;
import javax.swing.border.*;
import java.net.*;

public class BgImgScrollPane extends JScrollPane{
 private ImageIcon background;

 public BgImgScrollPane(Component view){
   super(view);
 }

 public void setBackgroundIcon(ImageIcon p){
   background = p;
 }

 public final ImageIcon getBackgroundIcon(){
   return background;
 }

 public void paintComponent(Graphics g){
   if (background != null){
     g.drawImage(background.getImage(), 0, 0, getWidth(), getHeight(),
this);
   }
   Border border = getViewportBorder();
   if (border != null){
     Rectangle r = getViewportBorderBounds();
     border.paintBorder(this, g, r.x, r.y, r.width, r.height);
   }
 }

 public static void display(Component c, URL imgUrl){
   JFrame f = new JFrame();
   f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

   BgImgScrollPane pane = new BgImgScrollPane(c);
   pane.setBackgroundIcon(new ImageIcon(imgUrl));
   pane.getViewport().setOpaque(false);

   JViewport column = new JViewport();
   column.setOpaque(false);
   pane.setColumnHeader(column);
   JViewport row = new JViewport();
   row.setOpaque(false);
   pane.setRowHeader(row);

   f.getContentPane().add(pane);
   f.pack();
   f.setVisible(true);
 }

 public static void main(String[] args) throws Exception{
   URL url = BgImgScrollPane.class.getResource("images/rose.gif");

   JTable table = new JTable(15, 4){
     public Component prepareRenderer
      (TableCellRenderer renderer, int row, int column){
       Component c = super.prepareRenderer( renderer, row, column);
       if (c instanceof JComponent){
         ((JComponent)c).setOpaque(false);
       }
       return c;
     }
   };
   table.setOpaque(false);

   BgImgScrollPane.display(table, url);
 }
}

The jar tool had used wrong directory and wrong files in it ????

see http://mindprod.com/jgloss/image.html
see http://mindprod.com/jgloss/resource.html

To track resource problems down, examine the jar to make sure the
resources are exactly in the jars named exactly as you planned with
perfect spelling and case.

use getResource and print out the URL to see if it is as you expected.

Narrowing down where it is screwing up is 80% of solving it.

Seems we are all stuck.
Will you try to make an extremely simple program
with a single class of which only method is main()
which accesses images/icon.gif file via
Class.getResource() method. Make a jar file for
the program and run java -jar command on it.

If the jar file do not run on your environment, put
it on a universally downloadable site. We will
try it on our environment. It will be better to
include the source file in the jar file.