XF 1.5 How to add background on a subforum?

[Rotary]

Hi,

how to add a background image on a subforum?

See picture: Instead the white I want make a background image.

 

[Rotary]

I tried it with this in extra.css
"
.node15 #header {
background: url("https://i.kinja-img.com/gawker-media/image/upload/qmybkmtqtg88gzoyltt1.jpg");
}"
(just taking a random picture link!)

But dont work for me

 

[OUTL4W]

Try this in extra.css

.nodeList  .node_15 .categoryForumNodeInfo, .nodeList .node_15 .forumNodeInfo, .nodeList .node_15 .pageNodeInfo,
.nodeList .node_15 .linkNodeInfo {
    background-color: transparent;
}
.nodeList .node_15{
    background: url("/path/to/image") no-repeat;
    max-width: 100%;
}