Marp markdown add custom background imgage to css styles

Question

Just recently i found out about marp. I want to customize it a little to have basically 4 types of slides. The title slide and the ToC slide should have different background images.

Following this post, i was able to customize the headings for those slides:

https://www.syndikat7.de/de/post/software-engineers-approach-to-presentation-slides

  section.title h1 {
     font-size: 60px;
     letter-spacing: 10px;
     margin-bottom: 0;
     padding-bottom: 0;
  }


---
marp: true
theme: mytheme
---

<!-- _class: title -->

# My heading on title themed slide

Now i want to add a cutom background image for the whole slide to this Class only.

But where do i have to but the background-image: url('PAth\to\image.png);?

if i put it in

section.title  {
        justify-content: center;
        background-image: url('PAth\to\image.png);
      } 

The image just shows up around the actual title. The slid backglround is unaltered.