Railpage does not support uploading photos from your own computer and embedding them in forum posts.
To post a photo in a forum post it has to be hosted on one of the many photo hosting sites available on the internet. Our personal favourite is Flickr, which has great integration with our Image Gallery, Locations, Locos and Routes modules.
You can add a photo to a post using the BBCode IMG tag. To do so, simply wrap the image url with IMG tags:
We like to make things easier for our users, so with Flickr photos if you post the URL to a photo page it automatically converts that into an embedded image Such as this example: