div#theme-image {

    width: 100%;
    height: 400px;
    overflow: hidden;
    margin-bottom: 10px;
    display: flex;
    flex-direction: row;
    align-items: center;
}

div#theme-image > div{
    flex-grow:1;
}
div#theme-image img {

    width: 100%;
    max-width: unset;
    display: block;
    
}