Just some tips for others about image signatures:
You can center them by using the center tags:
[center] [/center] And can add in URL's:
[url=http://www.mysigsite.com][img]insert imageurl here[/img][/url]
Note: adding in URL's into signatures are possible, they may need to be restricted as the URL can point to some other destination. When about to click on the signature image, let the mouse hover over it, pause and look to what the URL actually is (as seen in the lower right corner on the web browser). However, with the case here, there does not seem to be any users who would do such a thing. So it is a low risk here.
Note: I have opted out of providing a URL in my signature (which is why it doesn't work, even though I gave these tips). I think it takes away from the potential revenue from the in-post ads.