cartodb/assets/stylesheets/common/asset_item.scss

.AssetItem {
  display: inline-block;
  position: relative;
  width: 58px;
  height: 58px;
  margin: 0 20px 20px 0;
  overflow: hidden;
  border: 1px solid #DDD;
  border-radius: 3px;
  background: url($assetsDir + "/images/layout/loader_transparent.gif") no-repeat center;

  &:nth-child(12n) {
    margin-right: 0;
  }
}

.AssetItem .image {
  position: absolute;
  width: 60px;
  max-width: 60px;
  height: 60px;
  max-height: 60px;
  border-radius: 3px;
  background-repeat: no-repeat;
  background-position: center;
  line-height: 60px;
  text-align: center;
  vertical-align: top;
}

.AssetItem:hover .delete {
  display: block;
  opacity: 1;
}

.AssetItem.AssetItem-User.is-selected .image {
  top: 1px;
  left: 1px;
  width: 56px;
  height: 56px;
  background-color: #FFF;
}

.AssetItem.is-selected {
  border: 1px solid #BBD7F2;
}

.AssetItem.is-selected .image {
  background-color: #FFF;
}

.AssetItem .delete {
  position: absolute;
  z-index: 2;
  right: 0;
  bottom: 0;
  width: 14px;
  height: 10px;
  padding: 0;
  transition: opacity 100ms;
  border-top-left-radius: 2px;
  border-bottom-right-radius: 2px;
  opacity: 0;
  background: #333;
  background: rgba(black, 0.5);
  text-indent: 0;
}

.AssetItem .delete::before {
  content: ' ';
  position: absolute;
  top: 4px;
  left: 4px;
  width: 0;
  height: 0;
  border-top: 3px solid white;
  border-right: 3px solid transparent;
  border-left: 3px solid transparent;
}

.AssetItem.destroying:hover a.delete {
  display: none;
}

.AssetItem.simpleicon a {
  background-size: auto 24px !important;
}

.AssetItem.pin-maps a {
  background-size: auto 24px !important;
}