.image-container {
    position: relative;
    display: inline-block;
}

.main-img {
    width: 100%;
    display: block;
}

.stamp {
    position: absolute;
    top: 0px;
    right: 0px;
    z-index: 1;
}

img.stamp {
    width: 50px;
    height: 50px;
}