There should already be some good cinematic referents at the end of your Fae playbook; if there aren't, it's a shame they were cut.
Movies: [...] Labyrinth, A Midsummer Night's Dream (1999), Pan's Labyrinth
-- "Inspiration for the Fae", Urban Shadows English printing p.139
So whether your Fae is a goblin king and contact-juggling enthusiast, ill-met by moonlight, or just played by Doug Jones, you should probably assign them an approximately human size and shape. There are a couple of reasons for this.
The first is to be faithful to the broader inspirations, though given that you're asking this question I don't know if you have a lot of specific and relevant media experience. Urban Shadows bills itself as "a tale of supernatural drama and political intrigue set in a modern-day city" (p.8) and what that says to me is "TV drama shot on TV budget", where all of the characters are played by humans in makeup - no elaborate puppet rigs, no green-screening, no camera tricks to give a 7-foot vampire the same screen presence as a 7-inch fairy. Just human actors being dramatic at other human actors.
The second is to establish an appropriate tone. Because this is a tale of supernatural drama and political intrigue set in a modern-day city, your character is someone who already moves in the city's channels of power with its other major players, the vast majority of whom will have an approximately human size and shape. At any time you might find yourself needing to apply political pressure, call in favors, make veiled threats, make open threats, or descend into violence with one or more of these people. (Or, you know, kiss on them, if that's where the story's going and everybody's cool.) Is that something that everybody in your group is going to take seriously if one of the participants is a 7-foot vampire and the other is a 7-inch fairy? I mean, maybe it is, I can't say, it's not impossible and the Fables comics made it work for some people. But you shouldn't try to force it to be taken seriously, and you shouldn't perceive the game as trying to force you to take it seriously, either.