i.bootmodal-own-icon {
    background-image: url('../img/tinymce-icon.png');
}

i.mce-i-icon {
    font: 400 20px/1 dashicons;
    padding: 0;
    vertical-align: top;
    speak: none;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    margin-left: -2px;
    padding-right: 2px;
    background-color: #f00; 
    color: #0f0;
}