Gaile has made a page over at the official wiki where community members can guess what the third year birthday miniatures will be. Here is the link to that page.
Birthday miniatures are a Guild Wars tradition that started when the earliest made characters (April 28, 2005) turned one year old. Any character that has a birthday will receive a birthday present. The birthday present item contains one random miniature from the set of that year's birthday presents. A character created one year ago will receive a birthday present containing a miniature from the 1st year set, regardless of campaign or type (yes, PvP characters can receive birthday presents).
On April 28, 2008, Guild Wars will be celebrating its third birthday having sold over 4,500,000 boxes.