Once i decided to optimize product images and download them from FTP.
When i uploaded them back, i noticed, that some images got wrong.
Joomshopping didn't check for existing filenames, for example DSC001.JPG and DSC001.jpg - it different images. I know about *nix filesystems, it's ok and working right, but could be a problem for another OS, Windows or OS X.
I suggest to rename all files to lowercase before saving them on server. It would be much easier to work with local copy.