Service connect and dynamic image folder between parent site and child site

Hello there,
I have a main domain mymaindomain.com
I am using a folder called imagePr to store dynamic images from user with another domains (clients).
The user uses mymaindomain.com site to upload their picture and see the image on their site.

When I try to reach out the folder imagePr from the clientdomain.com to display the images it is not working unless I use the mymaindomain.com/clientdomain.com/gallery.php.

so, I created a unique project file for the client domain: I create the server connect to query the into from the database - The information was retrieved but when it comes to the image it is not showing because it is not in the client site but in the parent site.

Is there any way or better option or solution or suggestion to retrieve the dynamic images and display it on the client site? I am guessing so far that it is a path issue.
Any helps will be welcome.