You can add backgrounds, colors, images, music and about any HTML codes to your email. For the codes you need go to the HTML Codes page. These codes used are the same as the codes for making web pages. There are a few things you need to keep in mind when using HTML in your email sig. First, some computer browsers and email servers don't read HTML in their email. In that case your email would be blank. When you send an html email make sure the person's email can read HTML. If you are not sure just remove the signature from your email. I also wouldn't recommend putting too much stuff especially large files of images and music, in your email sig. The more stuff in it, the slower it loads. Also some email servers limit the size of files and emails that can be sent or received.
Some people prefer just a name, quote, thought or their web site address in their email signature. To do this you do NOT have to use HTML in your email signature box. Just type in your message or URL of your web site and it will be at the bottom of all your emails. All email servers can read this. If you are using your web site URL be sure to include http:// Most email servers will read it as a clickable link.
I also recommend having two email email addresses. One for receiving mail from places on the web that you have signed up for. Use the first email address because sometimes when you sign up for things on the internet your email address may receive unwanted email or even be sold to a spammer. Once you are sure you get no spam from an email address you can change that email address to another that is reserved just for known email senders and is spam free email.