[quote=@Shikaru]
What all in terms of races and gear is allowed? What kind of shops?
[/quote]
The answer to both of these is "any." That is, as long as it fits a general fantasy and/or steampunk theme. It's a place of worlds colliding, so anything goes, especially in terms of races and shops.

[quote]
Is it possible to make a thief character that steals from the other shops and has a black market of sorts?
[/quote]
I did actually write this with the thought of making a thief character myself. ;) As long as you're fair, go for it. The black market seems like it'd be hard, but if you can figure it out, again go for it! :) Character development and world building is what the East Market is here for.