mj-section-background-url-full.mjml

<mjml>
  <mj-body>
    <mj-section
      background-url="https://www.rust-lang.org/static/images/rust-logo-blk.svg"
      background-size="contain"
      background-repeat="no-repeat"
    >
    </mj-section>
  </mj-body>
</mjml>