How to show theme on front end before sign up for multisite

Use below code to get the theme screen shot and theme name at front end for multi-site sign-up page.

$themes = wp_get_themes();
foreach( $themes as $theme ){
  echo '<b>Theme Name:  </b>' . $theme -> name;
  echo '<div class="area"><img src="' . esc_url($theme->get_screenshot()) . '" /> </div>';
}