Well that's not really it. Fire bending also has the hot blue fire, earth bending has sand and mud (and Toph is the only metal bender), and water bending also has things like vines and stuff. It's really just the elements in different forms. Air is the most flexible, I guess, so it doesn't have any other forms.
The color of fire changes with heat with lighter colors (blue and white in particular) being the hottest. The reason Toph can bend metal is because she can feel the granules of soil in the metal itself. Water benders don't actually bend the plants, they bend the water inside of the plants.
As far as air bending goes, they can fly and I would trade in anything to have that power. Even though they do use gliders, Aang can still leap dozens of feet in the air and even control his movements midair so they still have some limited form of flight.
EDIT: I forgot about the hover ball scooter things they can create. They pretty much have limited flight without the gliders.