JSFiddle - React, Tailwind, and code Playground

HTML

<header>HEADER</header>
<!-- The image is 200 x 100 px: a green and a blue square next to each other. -->
<div class="container">
  <div class="tile">
    <img src="https://i.stack.imgur.com/qbpIG.png" alt="." />
  </div>
  <div class="tile">
    <img src="https://i.stack.imgur.com/qbpIG.png" alt="." />
  </div>
  <div class="tile">
    <img src="https://i.stack.imgur.com/qbpIG.png" alt="." />
  </div>
  <div class="tile">
    <img src="https://i.stack.imgur.com/qbpIG.png" alt="." />
  </div>
  <div class="tile">
    <img src="https://i.stack.imgur.com/qbpIG.png" alt="." />
  </div>
  <div class="tile">
    <img src="https://i.stack.imgur.com/qbpIG.png" alt="." />
  </div>
</div>
<footer>FOOTER</footer>

CSS

* {
  box-sizing: border-box;
}

body {
  display: flex;
  flex-direction: column;
  height: 100vh;
  margin: 0;
  background-color: lightgrey;
}

header,
footer {
  flex: 0 0 100px;
  background-color: tomato;
  display: flex;
  align-items: center;
  justify-content: center;
}

.container {
  flex: 1;
  min-height: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  grid-auto-rows: auto;
  padding: 3px;
}

.tile {
  display: flex;
  flex-direction: column;
  justify-content: center;
  min-height: 0;
}

img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  padding: 3px;
}