Hey there,
It seems that I can't replicate it in EasySocial of my local site and your site's login layout has the background image that you set it in the backend.
May I know which image do you want to update it and can you upload it to here so we can have a better check?
Perhaps it would be the best if you can update your FTP's access by editing the first post so that we can troubleshoot or you if needed.