Probably because the last time the board went properly tits up, it was because of ppl posting massive piccies and having huge, HTML rich sigs. It's not because they don't like you... :)
The only problem is that outside embedding isn't allowed, so you have to use a pic that exists on the Queenzone domain. Most people get around this by using their profile pic.
For other things like the scrolling text you mentioned, colors, etc.. I think it uses basic HTML but I could be wrong. I know you can't create a link.. it becomes a link only from the actual typed URL so you can't do your own text link or use a pic to link. So there are restrictions.
Best thing to do is mess around and try stuff, if you must. Some folks don't want 'extras' here, just conversation so that's why you've gotten the previous responses.