picture as the page background ?

Use a different Page Template for that page.

https://codex.www.ads-software.com/Template_Hierarchy

?? I’ve tried this already ….
that means I’ll need 20 different page templates ??
I though .. maybe .. there is some other trick ??

but thanks

Okay then, use a conditional tag, like is_page(). Could put a big set of them in your header file.