As you said it is a bit soon to make plans, but I think we will be doing some contest for sure. It will be a while before we get down to any sort of offical roles however, maby by beta 1 or 2.
Our goal is to make all the editors we use to make the full game available to modders, we also have a lot of plans to make it very easy to mod. If all goes well you should be able to create everything from spells and artifacts, to buildings, city units, and full maps. Creating original 3D characters will be more involved, and we are still working on ways to bring as much customization as we can fit in. As for shareing your creations Elemental will be leaps and bounds above anything we
Life and Death Magic are drawn from the same source in Elemental, but how they are used, and what spells are available to you are determined by your sovereign nature. If you are "Good" you get Life magic spells, if you are "evil" you get death magic spells.