I agree that there should also be elven structures(mainly in the city center) But i believe it wasnt really a trading city untill the men started inhabiting it (Numenorians and later gondorians) so more towards the coast there would be warehouses and banks build by rich human traders. Which i think could build like my concept: rich and detailed in layout like the references (Valetta Constantinople etc) but fitting somewhat the colour palette of their banner for the men that live there are proud.
Also what do you mean with decadent? That means immoral right? Do you mean decaying?