Different main wrapper background for each page of my website

Hello,
I am working on a website for a client and I would like to use a different main wrapper background image for each one of my pages.

I have already located the main wrapper in my style.css file:

.main-wrapper-main {

    background: #F7F7F7;
    background-image: url('https://opensolution.gr/wp-content/uploads/2013/02/background11.png');

I suppose that i should add lines of code for each page id, something like:

.page-id-xxx #wrapper {background-image:url(‘ImagePath&Name’);}

Does anyone know what code exactly should I add? Any help would be greatly appreciated.

My website is https://www.opensolution.gr