I am not sure what you're asking; is it not working to upload images?
It may depend on several things. Some free web hosting services do not allow particular file formats to be uploaded, or may have restrictions on them. I've seen this happen with mp3, but not with images, but it may depen don what format your images are in. There might even be a filter on their FTP server that prevents files with certain extensions from being uploaded. It may also depend on how your FTP software is configured; if you're going to be uploading images, you may need to make sure that file transfers are in binary, rather than ASCII or text format.
As for uploading web documents in Linux, you can use any number of FTP programs to accomplish this. lftp and ftp are two basic ones; gFTP is one that has a GUI for Gnome. Your distro probably came installed with one or more FTP applications.