.mce-i-lana-text-to-image {
    font: 400 20px/1 dashicons !important;
    line-height: 20px !important;
    background-color: #555d66 !important;
    color: #f5f5f5 !important;
    font-size: 15px !important;
    border-radius: 5px !important;
}

.mce-i-lana-text-to-image:before {
    content: "\f123";
}