I'm just curious about this name that is used for a city that devours cities? Even to insane cultists it seems a bit too odd. I would probably suggest Waking God, or other titles/names unless you are set on the name.
I have to admit I am rather fond of the name "Shaprat", but I am not averse to coming up with alternate names or titles for it. The way I see it, this entity is really beyond names - "Shaprat" is what some of its cultists call it, not what it calls itself (and it is doubtful if it actually calls itself anything specific).
I like this, its a very interesting design, I wonder though have you ever taken a look at the Manual of the Planes entry for Neth the Plane that Lives? It could provide some other ideas on how the city could operate as far as those who find it. Instead of just a static place where things happen.
I vaguely recall Neth. Though my primary inspiration for Shaprat were Carcosa as described by John Tynes' "Hastur Mythos" in Delta Green: Countdown as well as the movie "Dark City". I do plan to expand on Shaprat eventually, and in fact have provided more hints with the recent entry on the Brass Key. Though there are plenty of other aspects of Urbis I wish to expand upon… But I am glad you like it!