It would be impossible to really tell anything without seeing the map. Maps have to make "Sense" not just look good, little details like having a swamp next to a river or water area instead of in the middle of a desert for example. Large islands most often contain civilizations or at least the ruins of one. Maybe an ancient empire thousands of years old that was ravaged by a horrible plague or natural disaster and its inhabitants have turned savage and tribal. Maybe an educated clan of Lizardmen who have evolved to create a vast empire like the Garg's of Ilshenar. If it is remote then it might be savage, if it is close to any other cities or major trade areas then it would be simular in culture most likely. Then again you can always leave it empty with creatures whom it must be taken from and then the players can pick which path its evolution will take.
