The Square-Enix Member prize list has been announced today via the FFXIV's English language twitter and it would seem that the Ultimate Prize is an acrylic print of the primals poster revealed late last year.
These prizes are reserved for members who have registered enough Square-Enix products to earn their prize. It seems there's no word yet on exactly how many points you have to get to obtain this collector's item, but if you have a lot of S-E product registrations lying around that you haven't entered yet, now might be the time.
Just keep in mind that product registration codes do not come with downloaded games, only with new physical copies of Square-Enix games. If you're going to buy a bunch of games hoping to get in on the prize, you'll want to stick with buying a new physical copy.