Change background color or add image to search results page

Site URL: https://www.findliberty.net/search-tool

So theoretically easy question. When you visit: https://www.findliberty.net/search-tool, you see an image of a keyboard. But when you perform a search query, the image goes away and the white menus and logo are no longer visible because its a white background. I found another thread with a footer/header code injection but that didn't work. Any ideas? Prefer to have the image there, but if could just have a non-white background would be great tool.

Add to Code injection Header

<script>
if (document.location.pathname.indexOf("/search") == 0) {
    document.querySelector('body').classList.add('sqs-search-page')
}
  </script>
<style>
  body.sqs-search-page header.Header.Header--bottom {
    background-image: url(https://images.squarespace-cdn.com/content/v1/5953de722cba5e08ef12a358/1507834510203-6149A18DFD38L5IG6APF/ke17ZwdGBToddI8pDm48kFmfxoboNKufWj-55Bgmc-J7gQa3H78H3Y0txjaiv_0fDoOvxcdMmMKkDsyUqMSsMWxHk725yiiHCCLfrh8O1z4YTzHvnKhyp6Da-NYroOW3ZGjoBKy3azqku80C789l0iXS6XmVv7bUJ418E8Yoc1hjuviiiZmrL38w1ymUdqq4JaGeFUxjM-HeS7Oc-SSFcg/keybard+with+phone.jpg?format=1500w);
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center center;
    padding-bottom: 50px;
}
</style>

so whenever i try injecting the above into custom css it tells me there's a syntax error, i cant figure it out

18 minutes ago, BurningOaksNI said:

whenever i try injecting the above into custom css it tells me there's a syntax error

The code isn't CSS. It must be added to the Code Injection panel (within Settings > Advanced), not the Custom CSS panel.