header.header {
    background-image: url('/images/nicepage-images/damian-patkowski-T-LfvX-7IVg-unsplash.jpg');
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    min-height: 125px; /* or whatever suits */
}
.site-grid {
    background-color: #fadbb1; /* Light brown / tan */
}