If you want to add a background image for the header, you can use something like this (from the demo page)

#bhr-post-500 .bhr-header-wrapper {
    background-image: url('UR-IMAGE-URL');
    background-size: cover;
    height: 240px;
    background-position: center;
    box-shadow: rgba(0, 0, 0, .5) 0 0 0 100vw inset;
}

Where 500 in #bhr-post-500 is the ID of the business hours set, you can obtain that from the shortcode.