If you are sick of just the big 4 elemental planes, and scratching your head whenever an Ice Elemental is banished, try this arrangement.
The elemental nexus is a vast, expanding, sphere with gates to many, infinitely large, elemental planes at the edge. In addition to the big 4, Earth, Water, Air, and Fire, there are also, Metal and Wood on the sphere's equator. While there is a gate to the positive energy plane at the top, and the negative energy below, there are also a cluster of hundreds of small gates to the periodic elemental planes. The gate to the plane of Ice is midway between water and negative energy, next to the gate of ooze. Elemental planes are still being created, and the plane of plasma recently appeared between fire and positive energy.
The sphere contains a solar system formed from materials drawn from the planes, and is probably a work in progress.
The Elemental Plane of Wood? Oh my.
Problem is, wood is more of a "living matter" that others mentioned.
The Asian idea of the five elements is of a more spiritual nature that the common one, so i think this could not be possible.
You could make wood a part of earth plane though, or maybe a part an admixture of earth and water.
The Japanese society was an all boys club till just recently.
Instead of air they believed in wood and metal.
Ooze is usually produced organically. When an evil Gnoll druid summons a Wood Elemental, they will take an attack of opportunity if the characters start arguing science.
The strength of my cosmology is that you could have a plane of mud, and a plane of wood, both between earth and water.
http://www.dandwiki.com/wiki/Elemental_Plane_Of_Wood_(Keran_Plane)