I use xivpads.com's signature program -- it's in Beta and has a few bugs but once you figure out how to use it, it's a really great tool and updates reliably as opposed to the one I got from Enjin which never updated after I created it.

As an FYI you need to have a background image to upload and work with when using xivpads.com, this can be anything, but I created mine with the yellow border already on it and what not in a very simple graphics editor, it looked like this before the signature generator's items were put on it: