Forum only works with plain test with tags (like for image, urls and some formatting).
When I create lengthy posts with photos, I first crop and resize the photos, then I upload them to Photobucket. Next, I create a text file in the same folder where the photos are with a list of direct URL for all the photos. I also get rid of the "~original" tag on the end of each URL - sometimes that tag confuses the forum software). So make sure each URL ends in .jpg. Then I create a 2nd text file with the text of the write-up and there I copy/paste the image URLs where they belong, while also adding the IMG tag around them. The write-up itself can be initially done in any word processor, but it needs to be in plain text format for creating a TRW thread. That is why I use text file format for the version which is ready to be published.
Once all that is done I simply create a new thread in TRW and copy/past the entire text file. Since the text and image URLs are already properly arranged and formatted, the thread should look as you intended.