Adding Background Image Above or Behind Primary Navigation

Is it possible to add the colored shapes image above the site navigation?

If not above, how can I add it behind the navigation?

I found this in another thread which may solve your issue:

.header-announcement-bar-wrapper {
   background-image: url("https://static1.squarespace.com/static/5e8f40af1b4e4b61d7da3560/t/5e98a44ff7394c3f871aec65/1587061839876/sunman_tiny.gif") !important;
    background-size: cover;
    background-position: center center;
    background-repeat: no-repeat;
}

Obviously replace the url with your own