title: uitableviewcell custom background issue
body: <p>I have a grouped tableview where I have one row in each section. I am setting the backgroundview of the cell to my custom image and I wish the row is rendered this way:</p>
  
  <p><img src="https://i.stack.imgur.com/YykXO.png" alt="enter image description here"></p>
  
  <p>But it renders like this (notice the absence of shadows, it's flat):</p>
  
  <p><img src="https://i.stack.imgur.com/JwAxp.png" alt="enter image description here"></p>
  
  <p>Here's the code in cellforRowAtIndexPath:</p>
  
  <pre><code>((UIImageView *)cell.backgroundView).image = [UIImage imageNamed:@"BGImage"];
  </code></pre>
  
  <p>Where BGImage is the first image in this post, with shadows. What am I missing here?</p>