mj-hero-background-url.mjml

<mjml>
  <mj-body>
    <mj-hero background-url="https://cloud.githubusercontent.com/assets/1830348/15354890/1442159a-1cf0-11e6-92b1-b861dadf1750.jpg">
      <mj-text>
        GO TO SPACE
      </mj-text>
    </mj-hero>
  </mj-body>
</mjml>