title: Adding a background image to a panel containing other components
body: <p>I have a login form in Java panel, with user name / password fields.</p>
  
  <p>I would like to add a background image below this login-form.</p>
  
  <p>What is the best way to achieve this?</p>
  
  <p>Extra bonus for providing sample code, as I have a hard time figuring this out.</p>