.login-bg {
    background: url('https://d2kw2ya2fj5vbi.cloudfront.net/images/u1.jpg') no-repeat;
    background-size: cover;
}
.checkbox-Activity input[type="checkbox"] + label span {
    background: url('https://d2kw2ya2fj5vbi.cloudfront.net/images/check_radio_sheet.png') left top no-repeat;
}
.checkbox-Activity input[type="checkbox"]:checked + label span {
    background: url('https://d2kw2ya2fj5vbi.cloudfront.net/images/check_radio_sheet.png') -19px top no-repeat;
}