Yeah, what jhaelen just said. I very quickly imagined the Shaman as a spiritual oriented archetype.
Beastmaster, the animals of nature. The creatures and inhabitants.
Druid, the vegetation and growth of nature. The plants, water, and life.
Shaman, the spirit of nature. The energy that flows through life and connects it all.
So i could see Shaman having some incorporeal creatures.
Also possibly able to affect areas, like weather sort of conjurations.
Also, I'd say a Shaman would make sense as Nature, and Air school.
Could be cool as near Forcemaster levels of solo and arena manipulation with very few Shaman compatible creatures, like Forcemaster.