Magento2:: Image Field in system configuration

system.xml

<field id="logo" translate="label" type="image" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
    <label>Logo Image</label>
    <comment>Allowed file types:PNG, GIF, JPG, JPEG, SVG.</comment>
    <backend_model>Vendor\Module\Model\Config\Backend\Image\logo</backend_model>
    <base_url type="media" scope_info="1">folder/folder/logo</base_url>
</field>

/app/code/Vendor/Module/Model/Config/Backend/Image/Logo.php

<?php

/**
 * Copyright © 2015 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */

/**
 * System config Logo image field backend model
 */
namespace Vendor\Module\Model\Config\Backend\Image;

class Logo extends \Magento\Config\Model\Config\Backend\Image {
    /**
     * The tail part of directory path for uploading
     *
     */
    const UPLOAD_DIR = 'folder/folder/logo';

    /**
     * Return path to the directory for upload file
     *
     * @return string
     * @throw \Magento\Framework\Exception\LocalizedException
     */
    protected function _getUploadDir() {
        return $this-->_mediaDirectory->getAbsolutePath($this->_appendScopeInfo(self::UPLOAD_DIR));
    }

    /**
    * Makes a decision about whether to add info about the scope.
    *
    * @return boolean
    */
    protected function _addWhetherScopeInfo() {
        return true;
    }

    /**
    * Getter for allowed extensions of uploaded files.
    *
    * @return string[]
    */
    protected function _getAllowedExtensions() {
        return ['jpg', 'jpeg', 'gif', 'png', 'svg'];
    }
}