Is it possible for you to allow HTML code in forum signatures?

That might come down the road. But I'd offer it in posts before signatures.

Just a FYI your [url] code is not HTML code.. that is called BBC code.

HTML code would be like <a href="http://www.speedtest.com"><img src="http://www.speedtest.net/result/872201783.png"></a>;

I'd rather have BBC than HTML. Every forum I've been on has HTML banned, and BBC is also more user friendly.