.image-gallery-attachments {
    background: #fff;
    float: left;
    clear: both;
}

.image-gallery-thumbnail-wrapper {
    float: left;
    width: 19%;
    height: 45px;
    padding: 0.5%;
    overflow: hidden;
}

.image-gallery-thumbnail-wrapper img {
    height: auto;
    width: 100%;
    float: left;
}