Just to correct the author, in order to make a custom version of the splash page file, e.g. to modify the Author details or to e.g. add css classes etc, you will need to follow this:
1) Copy the file /wp-content/plugins/wp-maintenance-mode/views/maintenance.php
2) Drop it here: /wp-content/maintenance.php
3) Rename it to wp-maintenance-mode.php
You have to rename it because the author appears to have become confused with some coding in the file /wp-content/plugins/wp-maintenance-mode/includes/classes/wp-maintenance-mode.php on line 506
if (file_exists(WP_CONTENT_DIR . '/wp-maintenance-mode.php')) {
include_once(WP_CONTENT_DIR . '/wp-maintenance-mode.php');
} else {
include_once(WPMM_VIEWS_PATH . 'maintenance.php');
}
ob_flush();
Perhaps the author can correct that at some time in the future.