IPython/html/static/notebook/less/kernelselector.less

#kernel_selector_widget {
    margin-right: 1em;
    float: right;

    & > button {
        .btn-default();
        
        & > span.caret {
            margin-top:0px;
        }
    }
    
    & > img#current_kernel_logo {
        width: 32px;
        height: 32px;
    }
}