JSFiddle - React, Tailwind, and code Playground

CSS

* {
    margin: 0;
    padding: 0;
}
html, body {
    width: 100%;
    height: 100%;
}
body {
    background: url(//placehold.it/2000x2000);
    background-size: cover; /* Или "codver", поэксперементируйте */
}