Hi,
probably the image exists, in these cases is apache to manage the requests and send images so no way for joomla and redj to intercept and redirect the request. If this is not the case let me know and we will investigate further.

Maybe I was not clear. Let me try to explain better. When your web server receives a request like:

www.domainname.com/folder/subfolder/image.jpg

Or:

www.domainname.com/new/folder/subfolder/image.jpg

Then the web server first checks if the file exists. In this case it takes the file and send to the client. Joomla and ReDJ are not invited to the party at all.

Think to all static assets you get together with a page (CSS, JS, images, etc). They are all sent by the web server itself (except if you tell him something different, but this can be done with .htaccess file of httpd.conf or something similar).

The "Base path" is just a param that allows you to write rules without to take care of the current subfolder, so when you will move the site you will not have to change the rules (just the global base path param).

Kind regards,
Luigi