Может так:
https://jsfiddle.net/t5r4tqu1/1/
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
#gallery1{
position: relative;
}
#gallery1 .item{
display:inline-block;
width:24%;
padding:0;
margin:0 0 10px;
text-align:center;
}
#gallery1 .item img{
max-width:100%;
max-height:150px;
}
#gallery1 img:focus {
position: fixed;
top: 0;
left: 0;
bottom:0;
right:0;
margin:auto;
z-index: 31;
max-width: 100%;
max-height: 100%;
outline: none;
pointer-events: none;
}
#gallery1 img:focus ~ div {
position: fixed;
top: 0;
left: 0;
right: 0;
bottom: 0;
z-index: 30;
background: rgba(240,240,240,.9);
cursor: zoom-out;
}
</style>
</head>
<body>
<div id="gallery1">
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-1.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-2.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-3.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-5.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-6.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-7.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-8.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-4.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-9.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-10.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-11.jpg" alt="" tabindex="0" />
</div>
<div class="item">
<img src="http://mrsalvador.ru/old/img/superbox1/superbox-full-12.jpg" alt="" tabindex="0" />
</div>
</div>
</body>
</html>