I just posted one yesterday and it wasn't the most straight forward adventure.  I would bet others on this forum have a better way, but here is what I did.

I had my picture on my PC.  Then logged into Rancher.net and went to the photo gallery.  There I was able to upload a picture into the general gallery.  This got the picture on their server, and accessible on the web, which the post needs.  After you get your photo uploaded if you click on it to view, there will be a BBCode link in a box at the bottom of the page.  I copied it by hightlighting it and hitting CTRL C.  Then I went and made a post, and in the message I pasted the link with CTRL V, or right click and paste, and you  then have something that starts with .  It stays that way until you submit it and then it pulls in the photo.

It doesn't seem very slick for posting multiple photos, but it worked for my one.  That is why I am thinking others have a much better way of doing this.

Hope this helps.