What kind of site you are trying to publish images on.. html, jsp, or publishing software like joomla or wordpress?
Are you in charge of the server or are you "renting" a site?
As someone already said, i found several solutions, but it depends on what plattform You are running on and which possibilities You have the install/edit things on the server.
If you only want the latest pic it must be possible to publish a image and then get the camera-ftp client to overwrite that image...