There is also JPEG View which is really fast and simple image viewer for windows https://github.com/sylikc/jpegview (fork of unmaintained https://sourceforge.net/projects/jpegview/) and another one vjpeg http://stereopsis.com/vjpeg/
These are both small and fast image viewers, specially noticeable on very large images.
We need a list/directory of fast tools like these, specially now when every tool is bloated by default.