[quote=WizardGirl and SaraiRayne]
Yes, but has to have limits

Would only animals work?

Depends: Would they have full control, would they have all aspects
[/quote]

I have a few suggestions of limiting a shapeshifter power:
- limited use: takes up energy to maintain a shape
- doesn't change voice, intelligence, mannerisms. So it requires acting to make it convincing.
- does change voice, so no talking in animal form, just growling and hissing
- takes a while to change / is very painful
- movement not yet under control: animals that move radically different from humans are hard to control (cat or bear is doable, but a bird crashes)
- can only take shapes you know, you need to collect shapes and can only take shapes you've already collected. collecting is a ritual that takes time and effort.
or similar:
- can change into a creature you can see at that moment.
- there's a very obvious sign that can be recognized by people familiar with shapeshifters
- other animal's regard you as unnatural and will react hostile to you in any shape

maybe you can use something