.banner1 {
  background-image: url(/assets/images/banner-1.jpg)!important;
  height: 100%;

  display: block;
}

.banner2 {
  background-image: url(/assets/images/banner-2.jpg);
  height: 100%;

  display: block;
}

.banner3 {
  background-image: url(/assets/images/banner-3.jpg)!important;
  height: 100%;

  display: block;
}

.banner4 {
  background-image: url(/assets/images/banner-4.jpg)!important;
  height: 100%;

  display: block;
}

<div class="right_bx">


<span class="banner1"></span>

      </div>
 <div class="right_bx">
          <span class="banner2"> </span>
      </div>
 <div class="right_bx">
          <span class="banner3"></span>
      </div>
 <div class="right_bx">
          <span class="banner4"></span>
      </div>