Custom code to add a custom DropDown under rtMedia uploader.

functions.php

<?php
/*Here is the custom code to add a custom Dropdown under rtMedia uploader with a hiddenfield.
* You can add this code to your theme's functions.php file
*/
if ( ! function_exists( 'rtmedia_add_custom_dropdown_menu' ) ) {
    function rtmedia_add_custom_dropdown_menu( $content ) {
        ob_start();
        ?>

        <div id="custom_dropdown_list_wrapper">
            <select name="custom_dropdown" id="custom_dropdown_list">
                <option value="free">Free</option>
                <option value="paid">Paid</option>
            </select>
            <input type="hidden" id="custom_media_type" name="custom_media_type" value=""/>
        </div>

        <?php
        return ob_get_clean();
    }
}
add_filter( 'rtmedia_uploader_before_album_privacy', 'rtmedia_add_custom_dropdown_menu' );