Singular Background Across Whole Site

I'm noticing a trend in websites where there is a background image/element that sort of continues down the whole page, sort of getting rid of the idea of the sections.

Here are two examples:

https://knapsackcreative.com/

https://www.winc.com

Is something like this possible with squarespace? How might I go about trying to do something like this?

Or have I totally mis-described this and how would you describe it?

Thanks!

They used some section images to achieve this. eg this site https://knapsackcreative.com/, has this background (this site is Squarespace, so you can achieve it)

second site is not Squarespace