wagtail/client/src/components/Draftail/blocks/MediaBlock.scss

.MediaBlock {
    display: inline-block;
    position: relative;
    border: 0;
    padding: 0;
    cursor: pointer;

    &:focus {
        outline: none;
    }

    &__icon-wrapper {
        position: absolute;
        top: 0;
        right: 0;
        background: $draftail-editor-chrome;
        color: $draftail-editor-chrome-text;
        line-height: 1;
        padding: $controls-spacing * 2 $controls-spacing * 3;
        pointer-events: none;
    }

    &__icon {
        $icon-size: 1.5rem;
        width: $icon-size;
        height: $icon-size;
        font-size: $icon-size;
    }

    @mixin invalid-image-fallback {
        min-width: 256px;
        min-height: 100px;
        background-color: $color-grey-1;
    }

    &__img {
        @include invalid-image-fallback;
        display: block;
        width: 256px;
        height: auto;
        pointer-events: none;
    }
}