I updated the custom signature page which can be found under the Membership sub navigation item once you've logged in. In the new system you can change your signature using the WYSIWYG editor our forums have and also select a Signature for each active branch of the family. So each person can currently have 3 signatures.
Primary Gaiscioch Signature Example:
Elder Scrolls Online Signature Example:
Guild Wars 2 Signature Example:
With this feature you'll be able to use your custom signatures in multiple game forums and not worry about having a ESO signature on a GW2 forum or vica versa. Enjoy!