The .gif sprites?
The same as they put regular images in their signatures. They find a site that has them (like
here), right-click on them to get the information link (under View Image Info for me on Firefox), and then place that link in the [img]*[/img] tags.
So [img]http://dialgafans.pytalhost.de/Back/032sb.gif[/img]
becomes
Just make sure to keep the signature rules in mind while you're adding images, and you can check your signature
here.