MoeTalks

Thank you for this.  Searched for it and it worked.

Thank you for this.  You getting a coffee from MoeCritiqués.  
I was also able to make this work by using the below as well.  Both yours and the below worked.  I so appreciate your time.
.header {
background-image:url('image-url’);
background-repeat:no-repeat;
background-size:cover;
background-position: center;
}
 

Add to Design > Custom CSS
/* Icons to right */ .header-display-desktop { -webkit-box-orient: horizontal; -webkit-box-direction: reverse; -ms-flex-direction: row-reverse; flex-direction: row-reverse; } .header-actions.header-actions--left { -webkit-box-pack: end; -ms-flex-pack: end; justify-content: flex-end; }  

If you change the billing plan, and do not change the billing cycle, you will pay the difference between the two plans.

Wow, thank you for this.  This is great when the site is live and I have to do live updates, I can still work on it but no one sees it and then just remove the code.  Awesome

For the admin UI freebies, you can install it via Tampermonkey, which can help inject the user script into your website, follow steps in attached video. 
Note for Tamperscript: seeking for adviced if you are about to insert any of new scripts to your site
PS: in the tamperscript edit, make sure to update the @match line correctly, eg: your site url is https://denim-sturgeon-949p.squarespace.com/, then the value should be
// @match https://denim-sturgeon-949p.squarespace.com/*
Tamper.mp4

Unfortunately, this did not work for me because I am on a personal account. Is there anyway to get this to work on a personal account?