div.container div.content div.content-art-piece {
    /*align-self: center;*/
    /*width: 100%;*/
    margin: auto;
}

div.container div.content div.content-art-piece img {
    max-width: 780px;
    border: 1px solid black;
    /*width: 100%;*/
    /*height: 100%;*/
    /*margin: auto;*/
}