I'd also point out that Human Guise is a -0 power - and what can you do with powers? Why, you can tie them into items of power. So even a supernatural thing that has no natural excuse for shapeshifting can still get the human guise power... they just need a good story for why they have an appropriate artifact. Here's an example:
Talisman of the Frozen Mirage: Typically appearing as a simple silver brooch or cloak-pin, this item is always cold to the touch; when opened, it shows a picture of its current owner's true form, against a backdrop of glacial ice. Given the item's powers of illusion, any further details of its appearance are up to the current owner.
* Requirements: An aspect describing your character's connection to the winter fae you got the talisman from - something like "Three Favors Owed to Lord Talkoth" (if you traded for this artifact) or "Hunted by Malks" (if you stole it from someone), or, etc.
Note that this aspect can also be compelled when the talisman's limitations come into play - as a winter artifact, it can't make a realistic illusion of flame, nor can it conceal your shadow if that shadow is cast by firelight.
* Powers: Human Guise, Glamours
* Total Cost: -1 (Since the artifact grants glamours, it is by definition easily concealable, for a maximum bonus of +1 to offset the -2 cost of glamours.)