http://ff14sp.com/ffxiv-signature-generator/ it's one of the larger one with all the level info and stats, but I feel it's too big for this forums current layout. bare in mind that this site is in spanish so basically it goes like this:

First Name
Last Name
Linkshell
Server
Signature image appearance

http://www.enjin.com/tools/ffxiv-signatures is the one that I am currently using.