JSFiddle - React, Tailwind, and code Playground

HTML

<div class="square"></div>

CSS

.square
{   width:80px;
    height:80px;
    padding:10px;
    border:2px solid gray;
    background:lightgray;
}

.square::after
{
    content:' ';
    position:relative;
    display:block;
    width:100%;
    height:100%;
    bottom:0;
    right:-5px;
    background:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAMAAAAoLQ9TAAAAMFBMVEVSfMdukM7rWk+Ux1uYzGWl0nrTkWqpl4Oes9Sn1oTIs5jJ2a7u6pHx76zY58n7+vtposh+AAAAiUlEQVQYlS2OSRIEIQgEaREXQPj/b6fQyROVwUbWgYB9CepiUdgeY8g+VGVkIrfWxjmUm7tAyBNGKdy7ZT6h84kNMUtMCGNmyei1ZJZAC1tuOV5ZqS4Esh9tU1WJa4F1d9fKEMyR4Ze/EBxNW/ZUfWoHZoFytJndF6Y+AEWVUUZ+D0LbR0Qr6LJ+h5gITT0VdhUAAAAASUVORK5CYII=) right center no-repeat;
}