I've been successfully using the HTML Sandbox to post photos for years. For some reason, the instructions in the Sandbox no longer work for me. I don't know whether something has changed in how the FreeRepublic software handles those HTML instructions for posting images or whether something has changed in how my computer system sends those "post this image" instructions to FreeRepublic.
If you would, you might try to post an image using the HTML Sandbox instructions and check whether it works in the preview of your post. If your preview contains the image you tried to post, then the image posting problem must be in my system somehow. Let me know how it comes out, please. Thanks.