https://source.unsplash.com/featured?{keyword}

https://source.unsplash.com/collection/928423/480x480
<style>
body {
  margin: 0;
  padding: 0;
  background-color: #f6f6f6;
}
* {
  box-sizing: border-box;
}
img {
  width: 100%;
  height: auto;
}
.gallery-container {
  width: 100vw;
  height: 100vh;
  position: relative;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  padding: 10px;
}
.gallery-image {
  width: 25%;
  height: 400px;
  padding: 10px;
  background-color: white;
  box-shadow: 3px 3px 0px 0px rgba(0, 0, 0, 0.1);
  margin: 5px;
}
</style>
<div class="gallery-container">
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&1"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&2"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&3"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&4"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&5"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&6"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&7"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&8"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&9"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&10"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&11"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&12"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&13"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&14"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&15"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&16"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&17"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&18"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&19"></span>
<span class="gallery-image"><img src="https://source.unsplash.com/1600x900/?donkey,mule&20"></span>
</div>