@,
After reading your post more carefully, I now know what you are asking. You are asking how to add an image to your signature. All you have to do is click the image button in the formatting options. You will get a popup window like this: Paste the image URL in the URL box, click OK, and it should show up in your signature. Video Instructions:
Or if you are really lazy, copy and paste this into your signature.
[img=http://fc05.deviantart.net/fs71/f/2012/113/4/e/princess_luna__animated_signature__by_c3fear-d4xcdac.gif]