Prevent session from starting during WordPress pseudo cron procedures
wp-cron.php route triggers warnings:
[18-Jul-2020 05:54:32 UTC] PHP Warning: session_start(): Cannot start session when headers already sent in /path/to/wp-content/plugins/civicrm/civicrm.php on line 371
There's no need to start the session when running WordPress pseudo-cron.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information