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HTML 

              
                Probando
<div id="clouds">
	<div class="cloud x1"></div>
		<div class="cloud x2"></div>
	<div class="cloud x3"></div>
	<div class="cloud x4"></div>
	<div class="cloud x5"></div>
<!-- Cierre div al final para que se quede como fondo -->
<h1>Tucked corners for images (RWD)</h1>
<h3><a href="http://thecodeplayer.com/walkthrough/pure-css3-animated-clouds-background">The code player</a></h3>

<div class="esquinas">
  <img src="https://4.bp.blogspot.com/-xPRqOvYqvT8/U5g3mDeHgJI/AAAAAAAAQfU/9VHYS74AZnA/s500/iggy+pop+david+bowie.jpg"/>
</div>

<div class="esquinas">
  <img src="https://1.bp.blogspot.com/-7xrUdD8rVGY/VHJvXwc5YMI/AAAAAAAARuk/2XJYBpzFqss/s300/i%2Bsay%2Ba%2Blittle%2Bprayer%2Baretha%2Bfranklin.jpg"/>
</div>

<br/>

<h3> Four corners</h3>

<div class="esquinas">
  <img src="https://1.bp.blogspot.com/-jM0qKc9XeYI/U5g6YYGTYjI/AAAAAAAAQfc/EwDl93uScFo/s400/iggy+pop.jpg"/>
  <div class="esquinasbis"></div><!-- ADDED BOX -->
</div>

<div class="esquinas">
  <img src="https://2.bp.blogspot.com/-7QOgLRBuudU/UZJ0E3bTQhI/AAAAAAAAKGA/9A3hQD6h9RI/s800/million-dollar-quartet.jpg"/>
  <div class="esquinasbis"></div><!-- ADDED BOX -->
</div>
</div>
!

CSS 

              
                /* Photo album effect */
.esquinas {
  position: relative;  
  display: table;
  max-width: 90%;
  margin: 50px auto;
}
.esquinas img {
  display: table-cell;
  max-width:100%;
  height: auto;
  margin: 0 auto;
  padding: 8px;
  background: #fff;
  box-shadow: 0 0 2px #666;
  box-sizing: border-box;
}
.esquinas:before,
.esquinas:after,
.esquinasbis:before,
.esquinasbis:after {
  position: absolute;
  bottom: -20px;
  right: -40px;
  content: "";
  height: 40px;
  width: 80px;
  background: #ccc; /* Same color that wrapper background */
  box-shadow: 0 -6px 9px -8px #333;
  transform: rotate(-45deg);
}
.esquinas:after,
.esquinasbis:after {
  top: -20px;
  left: -40px;
  box-shadow: 0 6px 9px -8px #333;
}
.esquinasbis:before { 
  top: auto;
  left: -40px;
  transform: rotate(45deg);
}
.esquinasbis:after {
  left: auto;
  right: -40px;
  transform: rotate(45deg);
}

body {
	background: #ccc;
	margin: 0;
	padding: 0px;
}
h1, h3 {
  text-align: center;
}
/* Clouds effect */
#clouds{
  overflow: hidden;
	padding: 0;
  position: relative;
}

/*Time to finalise the cloud shape*/
.cloud {
	width: 200px; height: 60px;
	background: #fff;
	position: absolute;
  top: 300px;
  z-index: -1;
/* Opcional para que nubes salgan por encima
  z-index: 1;*/
	border-radius: 200px;
	-moz-border-radius: 200px;
	-webkit-border-radius: 200px;
}

.cloud:before, .cloud:after {
	content: '';
	position: absolute; 
	background: #fff;
	width: 100px; height: 80px;
	position: absolute; top: -15px; left: 10px;
	
	border-radius: 100px;
	-moz-border-radius: 100px;
	-webkit-border-radius: 100px;
	
	-webkit-transform: rotate(30deg);
	transform: rotate(30deg);
	-moz-transform: rotate(30deg);
}

.cloud:after {
	width: 120px; height: 120px;
	top: -55px; left: auto; right: 15px;
}

/*Time to animate*/
.x1 {
	-webkit-animation: moveclouds 15s linear infinite;
	-moz-animation: moveclouds 15s linear infinite;
	-o-animation: moveclouds 15s linear infinite;
}

/*variable speed, opacity, and position of clouds for realistic effect*/
.x2 {
	left: 200px;
	
	-webkit-transform: scale(0.6);
	-moz-transform: scale(0.6);
	transform: scale(0.6);
	opacity: 0.6; /*opacity proportional to the size*/
	
	/*Speed will also be proportional to the size and opacity*/
	/*More the speed. Less the time in 's' = seconds*/
	-webkit-animation: moveclouds 25s linear infinite;
	-moz-animation: moveclouds 25s linear infinite;
	-o-animation: moveclouds 25s linear infinite;
}

.x3 {
	left: -250px; top: 50px;
	
	-webkit-transform: scale(0.8);
	-moz-transform: scale(0.8);
	transform: scale(0.8);
	opacity: 0.8; /*opacity proportional to the size*/
	
	-webkit-animation: moveclouds 20s linear infinite;
	-moz-animation: moveclouds 20s linear infinite;
	-o-animation: moveclouds 20s linear infinite;
}

.x4 {
	left: 470px; top: 150px;
	
	-webkit-transform: scale(0.75);
	-moz-transform: scale(0.75);
	transform: scale(0.75);
	opacity: 0.75; /*opacity proportional to the size*/
	
	-webkit-animation: moveclouds 18s linear infinite;
	-moz-animation: moveclouds 18s linear infinite;
	-o-animation: moveclouds 18s linear infinite;
}

.x5 {
	left: -150px; top: -150px;
	
	-webkit-transform: scale(0.8);
	-moz-transform: scale(0.8);
	transform: scale(0.8);
	opacity: 0.8; /*opacity proportional to the size*/
	
	-webkit-animation: moveclouds 20s linear infinite;
	-moz-animation: moveclouds 20s linear infinite;
	-o-animation: moveclouds 20s linear infinite;
}

@-webkit-keyframes moveclouds {
	0% {margin-left: 1000px;}
	100% {margin-left: -1000px;}
}
@-moz-keyframes moveclouds {
	0% {margin-left: 1000px;}
	100% {margin-left: -1000px;}
}
@-o-keyframes moveclouds {
	0% {margin-left: 1000px;}
	100% {margin-left: -1000px;}
}
!

JS
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