Something you aren't doing right.
The image and the directory it is in must have read and write permissions for the webserver which is usually a different user than the ftp user. You can take ShopSite entirely out of the picture by trying to view the image by going to
http://<yourdomainname>/media/<imagename>.jpg in your browser. If you can't see it then you definitely have a permissions problem since that would not involve ShopSite in any way. When you uploaded the image by ftp you may have created a file that couldn't be viewed or deleted from the ShopSite interface. Try uploading a different image using the ShopSite Image upload functionality and see if you can view that image.