title: UITableView background image for content
body: <p>I have UITableView with height = 1000px, I need to set scrollable background.
  I know how to set background image for tableview but in this case that background image will not be scrollable.</p>
  
  <p>Right now the only idea how to do that is:
  1) create scroll view with proper height (about 1000 px), and set background image for that scroll view. then set frame of UITableView as the bounds of scroll view (and disable scrolling for UITableView). </p>
  
  <p>But my idea is rather bad, because I have many cells with many images on them, and in my approach all the cells will stay in memory.</p>
  
  <p>What is the best way how to implement scrollable background inside tableview?</p>
  
  <p><strong>P.S.</strong> </p>
  
  <p>I have tableview header of unknown height (depends on the response from server)</p>