With the old post tools, there were ways to post HTML, which allowed you to link to an image that wasn't on Giant Bomb.
This was very useful for the Giveaway Thread, as it allowed us to use the dynamically updated images provided by Steamgifts. These images let people know if a giveaway was still running, how long it had left and how many people had joined in already.
I would like to have this feature back in some capacity. Perhaps when you click on the Img button, the URL Address option would have a checkbox to, "leave image on external server".