.custom-yoga-feature i, 
.custom-yoga-feature .icon,
.custom-yoga-feature [class^="theme-icon-"] {
    background-image: url('PASTE_YOUR_COPIED_MEDIA_FILE_URL_HERE') !important;
    background-size: contain !important;
    background-repeat: no-repeat !important;
    background-position: center !important;
    width: 50px !important;  
    height: 50px !important; 
    display: inline-block !important;
}