Unfortunately, the provided search results do not contain any information about creating a PNG background with an "NFL Alumni | Supporting Former Players" image.

However, I can suggest some possible approaches to achieve this using Gatsby and React Helmet:

1. Use a library like gatsby-plugin-react-helmet to manage document head data.
2. Create a custom component that uses the react-helmet API to add a background image to the HTML document.

Here's a simple example:

import { Helmet } from 'react-helmet';

function NFLAlumniBackground() {
  return (
    <div>
      <Helmet>
        <style>
          /* Add CSS styles to apply the background image */
          body {
            background-image: url('https://example.com/nfl-alumni.png');
            background-size: cover;
            background-position: center;
          }
        </style>
      </Helmet>
      <!-- Your content here -->
    </div>
  );
}

Note that this is just a starting point, and you may need to adjust the CSS styles and image URL to fit your specific requirements.

If you're looking for more advanced solutions or want to explore other options, I can try to help with that as well!