<div id="cover">
  <img src="https://imgur.com/dv9Z2Nu.jpg">
  <img src="https://imgur.com/htWKe9m.gif">
  <img src="https://imgur.com/eog5eFZ.gif">
  <img src="https://imgur.com/nUJVBmO.jpg">
</div>

body {
  background-color: #343434;
}

#cover {
  width: 800px;
  height: 800px;
  margin: 0 auto;
}

#cover > img {
  float: left;
  border: 2px solid black;
  width: 45%;
  margin: 1.66%;
}