.js-product .t-product__option-variants_buttons .t-product__option-checkmark_image {
    border-radius: 5px;
    height: 100px;
    width: 100px;
}

.js-product .t-product__option-variants_buttons .t-product__option-input:checked+.t-product__option-checkmark_image:before {
    border-radius: 5px;
}