Dear ridgeback,
Please check the path of gallery folder, the default gallery folder is "GalleryFiles", in download package, you can find this folder, some image files and configuration files can be found in this folder. When you open dotnetgallery, it will display these image files. Please check whether you have removed image files in gallery folder, if all image files have been removed in gallery folder, no image files will be displayed in gallery.
You can change gallery folder path in web.config, please open web.config,
You will find:
<!-- <add key="DotNetGalleryFolder" value="~/GalleryFiles/" /> -->
You can uncomment it and change it to your own folder.
Regards,
Eric