Since version 3.5, WordPress no longer allow user to change media upload folder from admin dashboard. To change user have to edit “wp-config.php” file located in wordpress intallation folder
If you want to change the upload folder like http://www.example.com/wp-content/images/, you have to add the following code in “wp-config.php”
define( 'UPLOADS', 'wp-content/'.'images' );
If you want to change the upload folder like http://www.example.com/images/, you have to add the following code in “wp-config.php”
define( 'UPLOADS', ''.'images' );
You can still choose whether or not you want uploaded files to be organized in month/year folders in Settings » Media.