.node--type-image-gallery div div {
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
}

.node--type-image-gallery img {
  width: 300px !important;
  height: 200px !important;
  box-shadow: 1px 1px 4px rgba(0, 0, 0, 0.4);
  padding:5px;
  margin:10px;
}