html,
body,
.section-images {
  height: 100%;
  margin: 0;
}
.section-images {
  margin: auto 2em;
  text-align: center;
}
img {
  display: block;
  width: 60%;
  height: 60%;
  max-width: 100%;
  max-height: 90%;
  margin: 20px auto;
}