1) Not sure, but I think it has something to do with making lots of posts and getting lots of thumbs up.
2) Upload it to an image sharing site such as http://tynypic.com/ and post the link at the end of your message. With tinypic.com it is either the "HTML for Websites" or "IMG Code for Forums & Message Boards" link.
3) Click "My Account" at the top right of the page, near the flag. Then type in the comment you want in the "Signature" field at the bottom of the page.
VLA Price at posting:
59.0¢ Sentiment: None Disclosure: Not Held