wcfm-custom-field-image-type-upload

function isImage($url) {
    $headers = get_headers($url, 1);
    if (isset($headers['Content-Type'])) {
        $contentType = $headers['Content-Type'];
        if (strpos($contentType, 'image/') === 0) {
            return true;
        }
    }
    $pathInfo = pathinfo($url);
    if (isset($pathInfo['extension'])) {
        $extension = strtolower($pathInfo['extension']);
        $imageExtensions = ['jpg', 'jpeg', 'png', 'gif', 'bmp', 'webp', 'ico'];
        if (in_array($extension, $imageExtensions)) {
            return true;
        }
    }
    return false;
}

add_filter('wcfm_custom_field_value', function($val, $name, $product_id, $field_type, $field) {
    if($field_type == 'upload') {
        $field_value = wcfm_get_attachment_url(get_post_meta($product_id, $name, true));
        if(!$field_value || !isImage($field_value)) {
            return $val;
        }
        return '<img src="'.esc_url($field_value).'" alt="'. wcfm_removeslashes(__($field['label'], 'WCfM')) .'"/>';
    }
    return $val;
}, 10, 5);