Setting Background Of JScrollPane?

My program's tree:

JFrame{
JPanel(That MenuBar at the top)
JPanel(That panel at center with table){
JScrollPane{
JTable
}
}
}

I want to add my custom image to that grey space right there. I guess it is a JScrollPane, because I added that orange background on JPanel that contains it. But when I add this code to my custom class of JScrollPane:

@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
if(background == null){
background = new ImageIcon(ClassLoader.getSystemResource("tableBg.png")).getImage();
}
g.drawImage(background, 0, 0, null);
}

The result is the same, no changes.

Then I read some documentation. I found this method:

scrollPane.getViewport().setBackground(Color c);

It works, but it accepts only color and I want to add image. Is there any way to do that? Do I need to subclass JViewport and use paintComponent ? If yes, then how to make getViewport() method return my custom subclassed version?