if memory serves me correct your images are not saved to iPod as a jpg/gif etc they are saved as a different file type but I cant remember the directry but having a quick nose I came across /private/var/mobile/Media/Photos I think this is the directory your after
if memory serves me correct your images are not saved to iPod as a jpg/gif etc they are saved as a different file type but I cant remember the directry but having a quick nose I came across /private/var/mobile/Media/Photos I think this is the directory your after