.wp-list-table .column-avatar img,
.wp-list-table .column-username .avatar { 
    border-radius: 50px !important;
}

#wpadminbar #wp-admin-bar-site-name>.ab-item .site-icon,
#wpadminbar #wp-admin-bar-my-account.with-avatar>a img {
	background: none !important;
}