Visitors that have JavaScript disabled means practically:
- Screen readers for blind people - I don't see a reason they should download images
- Some bored admin viewing page with text-mode browser - no images downloaded as well
- Google BOT or some other bot crawling pages - they would do with the links what they want, for example ignore it
- Scripts writing the page for offline usage, that would save the image or not, depending on the settings (in most cases not)
The only place where such image-tracking could have work are the HTML mail messages, but such images are normally blocked, or you could fall under spam filter.