The Dragon Isles are a group of islands which are, so far, only represented as a piece of unnamed art in The Art of World of Warcraft and as a set of unfinished render models hidden in WoW data files called "Dragon Isles". The model was in-game during the Beta testing in a zone called Designer Island. The art was also used in the original WoW credits.
In World of Warcfaft: Looking for Group Documentary, released at Blizzcon 2014, early concept of Eastern Kingdoms was shown. And there is zone named "Dragon Isles: 65-70+ Raid' can be seen.
It is speculated that these might have something to do with the naga and their capital of Nazjatar, although Nazjatar is supposed to be built underwater, not on an island. However, it could as easily be speculated that they have, in fact, something to do with the dragons (hence the name) and perhaps be the home of one of the dragonflights.
The Dragon Isles' most significant feature are shells of monstrous sea creatures. It has also been speculated that, because of their monstrous size and resemblance to what can be found at Master's Glaive, they might have something to do with the Old Gods.
The Warcraft RPG book Shadows & Light might hold a clue as one of its short stories is about a group of adventures that had plans to build a device to raise Nazjatar to the surface of the ocean. It raises the question as to whether the palace could be brought to the surface. If they managed, it may have become the island in the concept art.
The Dragon Isles artwork is possibly inspired by the Illithid Spaceships known as "Nautiloids" from the Spelljammer campaign of Dungeons and Dragons, and could have been used as a vehicle of some sort, similiar to a giant turtle battle sub.
In Warcraft II EditThis section concerns content exclusive to Warcraft II.
The mysterious Dragon Isle was also a location in a Warcraft II multiplayer map, and was shaped like a dragon's head.