No, Cedric, you misuderstood. If you have an image hosted elsewhere, you can post it here by simply enclosing it in the img bb code tags. That makes the image appear in the thread just as it always has. If you use the url tags instead of the img tags, it will make a text link to your image.
The upload limit is only affected when you add an image to a post using the "add attachment" button. That uploads your image to this server and gives it a url on this domain that you can link to elsewhere if you like. That uses my bandwidth, which costs me money. I can't afford to give everyone unlimited free uploads, hence, the limit, which is vastly increased for those who would like to contribute funds.
It is simply a way to thank those who contribute by allowing them to store lots of files here. It does not affect those who don't care to contribute. They can just use third party file storage sites like photobucket, just as everyone did before I added the attachment feature.