If the island in Lord of the Flies is considered a character, what traits does the island possess?

There are many ways one could view the island in Lord of the Flies if it were to be considered a character. Two of those are that the island would be another littlun or that the island would be a permissive parent. 

The island and the littluns have much in common. Both are natural and operate on an instinctive level, without much or any rational thought. We might say that both start out with pure and innocent hearts. The littluns have no malice for anyone; they are content to eat and play. Simon finds a peaceful hideaway in the jungle that could be compared to the island's heart; it is a contented and sweet-smelling place representing the untouched innocence of nature. The island, just like each of the littluns, deserves to be appreciated just because it is a unique creation. When the Ralph, Jack, and Simon explore the island in chapter 1, they find a bushes with "candle buds." Ralph and Jack disparage the buds because they have no utilitarian value. "You could't light them," Ralph says, and "We can't eat them," says Jack. Yet Simon realizes they are special just because they are, and he names them. In the same way, the older boys tend to ignore the littluns and don't even learn their names because they don't contribute to the society. As the novel progresses, both the littluns and the island suffer at the hands of the older boys as they descend into savagery. At least one littlun is killed, and the others are taken over by Jack when he creates his own tribe. Similarly, the heart of the island, Simon's getaway, becomes corrupted by the boys when they place the pig's head on a stick next to it. Eventually, the boys use the island to carry out the murder of Piggy by rolling down a big rock on him. And at the end of the book, the island is in danger of being destroyed by fire from the boys. Although both the littluns and the island begin in innocence, they are sucked in and contaminated by the savagery of the older boys.

Another way of viewing the island as a character is to think of it as a permissive parent. It provides everything the boys need for their physical lives, but it provides no instruction or guidance to them with regard to their social or spiritual development. This absence of moral training creates a vacuum which can be filled by darkness and evil. Golding shows that children who are left to their own devices without moral guidance will descend into savagery. Parents who provide for a child's physical needs and ignore their moral training may find that moral depravity will eventually lead to the child's destruction. 

Depending on one's preference, the island could be a littlun or a permissive parent.