Кнопка поверх изображения-ссылки

*{ 
  box-sizing:border-box; 
} 
.picture{ 
  position:relative; 
  display:inline-block; 
  width:100px; 
  height:100px; 
  background:url(//i.stack.imgur.com/JkEWk.jpg) no-repeat center/cover; 
} 
.picture__link{ 
  display:block; 
  position:absolute; 
  top:0; 
  left:0; 
  width:100%; 
  height:100%; 
  z-index:1; 
} 
.picture__button{ 
  display:inline-block; 
  position:absolute; 
  top:5px; 
  right:5px; 
  z-index:2; 
  background:none; 
  border:1px solid; 
  font-size:20px; 
  font-weight:bold; 
  color:#fff; 
}

<div class="picture"> 
  <a href="#" class="picture__link"></a> 
  <button class="picture__button">✕</button> 
</div> 
<div class="picture"> 
  <a href="#" class="picture__link"></a> 
  <button class="picture__button">✕</button> 
</div> 
<div class="picture"> 
  <a href="#" class="picture__link"></a> 
  <button class="picture__button">✕</button> 
</div>