Ok, i tried it your way, still utterly breaks everything to look ugly. You do not need to input /forums/ as when your img sourcing it goes by the root of the forum, not the site.
Your Way
My Way
Now from my point of view, my html code works, not saying yours doesn't, but then look up to the first image and see for yourself. I didn't change any plugincode, and the html i used was what you posted, just changed the xx's to the id and oo to style. My problem could be due to the style i a using though, but all in all, this shouldn't happen regardless, especially for a mod like this.