Custom background

i’m looking to customize the background of my site. It’s curently in dark color and i would like to put an image instead.
basically, the fonction to customize the background in WP dashboard (in appearence) is locked/not visible, but i can unlock it by adding CSS in the function.php page.
I can now custom the background image in WP dashboard but despite this the background image is not displayed (i can see it stealthily when i change pages).

can someone help me to display the background image or telling me where can i activate it? (like in the style.php page)

Hi, @ccauquais

What is the link to the website where you want to apply this change?

Here is the link to the website i wanted to change the background

@ccauquais can you try this workaround?