I think that the Shaman's spirit animal should not be identical to the wizards familiar. The main reason for this is that i think of spirit animals as the big north american animals more often than small ones; elk, bison, bear, wolf, etc. However simply giving them a druid animal companion would not work as that is a significantly more powerful ability. So I have tried my hand at making a Spirit Animal alternative to the familiar ability, hopefully it is balanced, likely it is not. I have yet to actually use a shaman but was looking at making one as an NPC but wanted them to have a bison companion sooo....
Spirit Animals for Bardarokian Shamans
Breakdown over 20 levels
Loose: Familiar Special Ability, Alertness, Improved Evasion, 3 points of intelligence, scry on familiar
Gain: Change from familiar base list to animal companion base list (first form only), +3 Str, +3 Dex.
As a related side note for animal companions wolves should be small and bears should be medium not the other way around. Because that's how big wolves and bears are.
bump
Hello. Unfortunately I don't have the ACG yet, so I had to look up the Shaman on the d20pfsrd. I think that since the shaman class is a hybrid of arcane and divine classes. Therefore, I think that spirit animals should be a hybrid of familiars and animal companions. They should have their own unique progression.
I saw on another thread that someone suggested that a character take the fox and reflavor it as a wolf cub, and then take the improved familiar feat to make it an actual wolf at third level.
Perhaps this idea can be incorporated into the spirit animal progression table. That, like animal companions, spirit animals become larger as time goes on. Not as large as their animal companion counterparts can become, but larger than a familiar.
As for what else should go in the progression, got me. I'm in favor of keeping the extra intelligence points over the physical stat boosts because spirit animals are spirits.