When you provide a full path of a local picture, the generated show will display the pictures in this folder. Your pictures are not uploaded to the server, the path you provide is only used to generate the show file. An example of a full path is D:\MyPictures\Picture001.JPG
Be careful with lots of high resolution pictures. This can result in long loading time, bad performance and out of video memory errors. It is best to create a temporary folder with prepared pictures.