Alright, this is a suggestion for a proper *new* race to the realm of Eorzea!
Now, I know a lot of people have been clamoring on about Viera, but honestly, I think they would be a pretty poor choice. The reason is simply that I think their appeal can be found in several of the existing races; they're basically taller Miqo'te who trade cat traits for rabbits'.
Not that the Viera are a *bad* race, mind you, merely that they're a bad *choice* for the first new race. Instead, we need something that strikes an altogether different visual-appeal than any of the existing races.
Enter: the Esperkin
My thinking is a race of bestial humanoids. Perhaps formerly having been of Elezen descent, they're a people who were totally isolated to previously unknown land, whose use of Summoning and other dangerous magicks have eventually caused them to evolve into something wholly different, and even their cultures having splintered into two distinct Tribes. These two tribes have waged war in the past, and while still suspicious of the other's motives, agreed to a peace treaty.
The first is the Feral tribe. I'm basically thinking these guys would look exactly like Behemoths, but standing upright, and far thinner, more athletic. Leaning towards brute-force, they would be extremely lean, having developed razor-sharp talons over countless centuries, losing almost any evidence of their Elezen heritage. They would be a tribe of honorable savages and reckless warriors, who value might above all else, finding natural allies in the city-state of Ul'dah.
The second is the Noble tribe. These guys would be build much more closely to Odin; very tall and noble-looking, keeping much closer to their Elezen roots. However, they too have been influenced by centuries of magic-use, but are far more benevolent in its practice, as they now stand atop cloven feet (read: hooves), and have majestic, ornamented antlers jutting out from their heads. Being far more peaceful and prone to democracy over force, and also having a healthy respect for nature, would find Gridania to be as good a home as any.
So, let's get into more specific details.
Firstly, they would all be bi-pedal. That is, their legs would have the same general shape as a dog's hind-legs, assuming you know what a dog looks like :P. Both would probably be completely fur-less, with Noble tribe having cloven feet (hooves), whilst Feral tribe would have prominent claws.
Noble tribe would be able to borrow almost all of its hair-styles from existing choices, though perhaps adding more long-hair options. As well, they would have several choices of Antlers, and choice in decorating their with beads, trinkets, or even gilding them with gold or silver. Their skin-color would probably range from a golden-bronze to a gunmetal-black.
Feral tribe would be much different, as all of their "hairstyles" would connect to a large mane that trails down their back. Their heads would probably also sit a bit higher, giving them a "less-human" silhouette, as well as having horns instead of antlers. While their heads and color-schemes would borrow from Behemoths, they would actually still be quite thin, but just insanely-defined muscles, giving them almost a "were-wolf" vibe. Their skin-tones would probably go through various shades, bright and dark, of red, blue, and purple.
For their cultures, I would split them up based on their tribes. The Feral tribe would be more nomadic, having no real "architecture" to call their own, mostly just tents and huts. They would definitely be the more rugged of the two, and have a culture that revolves around fighting for honor. As such, they would have no City-State to call their own, but might find themselves in Ul'dah more often than the other capitals. Warriors and Black Mages would be staples of their tribe (although no in-game benefit for being such).
In contrast, the Noble tribe would be much closer to things we've seen before. They would prefer great, lavish castles and stone-work. Over countless centuries, they banded together an created a keep whose magnificence has never been rivaled! However, some years ago, their High King began to slip into madness, holding executions of any who questioned his rule. As such, the Esperkin were forced to find allies elsewhere in Eorzea to help take back their once-glorious kingdom. In the meantime, they would find refuge in Gridania. Paladins and Summoners would be staples of this tribe (although again, no in-game benefit for being such).
And, taking things a step further;
With the introduction of the Esperkin race, we would also see the introduction of the Dark Knight job. While the two Esperkin tribes waged war in the past, they eventually struck a peace-treaty. While both tribes generally remain isolation from one another, there were some who sought to train alongside one another, eventually culminating in the Dark Knight. Weaving the dangerous magicks that created their race, with the marryment of the Nobles' brilliant tactics and the Ferals' unending rage, they would wield Two-handed Swords with attacks augmented by dark magic.
Now, since I don't really know as much about how such a class might play in FFXIV, I'll leave it to more experienced players to dictate what sorts of abilities they might use (I mostly wanted to tie a bit of Lore in with the Class). Instead, I'd like to add a couple of pictures, just to give some visual-aid of the *idea* of this new "Esperkin" race.
Feral Esperkin (keeping in mind; human-like torso, beastial head and legs):
http://img2.wikia.nocookie.net/__cb2...oth_render.png
http://img3.wikia.nocookie.net/__cb2...BahemothXV.jpg
http://img4.wikia.nocookie.net/__cb2...viii-ifrit.jpg
Noble Esperkin:
http://img2.wikia.nocookie.net/__cb2...FFVIII_Art.jpg
http://img4.wikia.nocookie.net/__cb2...2/FF8_Odin.png
http://img2.wikia.nocookie.net/__cb2...CFF7-Ifrit.jpg