Elemental Characteristics
Fire elementals are characteristically ill-tempered and will not hesitate to hurt anybody when angered or provoked. Can oftentimes be rather capricious, as they're not constantly angry all of the time. A lot of Fire elementals are generally pretty nice and normal people when they're not angry.
Water elementals are characteristically calm, collected, and smooth. They don't enjoy harming people, but they are definitely capable. They hardly ever get angry or lose their cool to the point where it's a huge break in character. They are quick to recompose themselves whenever they do happen to lose their cool, however.
Earth elementals are characteristically emotional. They are more melodramatic than any other element, besides sometimes Aether. Not only are they ill-tempered like a Fire (although not as ill-tempered, per se; it's definitely safer making an Earth mad than it is making a Fire mad), but they are also quick to become sad, happy, excited, etc.
Air elementals are characteristically easygoing and laid back; so much so, sometimes, that they could even be pushovers. Pushover Airs are certainly not uncommon, and although there are more Airs in the world than any other element, they die at a quicker rate than any other element. This is because rotten people enjoy using and taking advantage of Airs for their own personal gain.
Aether elementals are characteristically dark and scary; powerful and crazy. They don't care what they do, nor what others do. It doesn't matter to them. A lot of Aethers have differing personalities, more so than any other element. Either way, it's definitely safe that all of the Aethers don't reside on Earth. The fewer, the better.