img overlay

<div id="box">
 
  <div id="overlay">
    <span id="plus">x</span>
  </div>
 
</div>


body    {  background:#e7e7e7;}
#box    {  width:300px;
           height:200px;
           box-shadow:inset 1px 1px 40px 0 rgba(0,0,0,.45);
          border-bottom:1px solid #fff;
          border-right:1px solid #fff;
          margin:5% auto 0 auto;
          background:url(http://ianfarb.com/wp-content/uploads/2013/10/nicholas-hodag.jpg);
  background-size:cover;
border-radius:3px;
overflow:hidden;}

#overlay    {  background:rgba(0,0,0,.75);
               text-align:center;
               padding:45px 0 66px 0;
               opacity:0;
               -webkit-transition: opacity .25s ease;
-moz-transition: opacity .25s ease;}

#box:hover #overlay {
               opacity:1;}

#plus       {  font-family:Helvetica;
               font-weight:900;
               color:rgba(255,255,255,.85);
               font-size:96px;}