Hello,

Please add this code to the Theme Settings > Custom CSS

.single-product-content > .container {
    max-width: 100%;
    width: 100%;
    margin-top: -40px;
        margin-bottom: 0!important;
    padding-top: 40px;
    padding-bottom: 40px;
      background-image: url(https://www.fjallraven.co.uk//media/i/2240x1320_General-background_photo_lassic16_6880-14296-0.jpg);
        background-position: 50%;
        background-size: cover;
}
.single-product-content .product-image-summary-wrap {
    max-width: 1192px;
    margin-left: auto;
    margin-right: auto;
}

Best Regards