There are even sacred druid sites in Sharn, so it's not that unusual.
The warforged should either stick to the basic plating or take Ironwood Body (Races of Eberron). I'd choose the former.
For animal companion, I'd choose a flying one, probably an eagle or owl (if you focus on the outdoors) or a bat (if you focus on the caverns below Sharn). Other than that, a dire rat should be the most common-sighted animal companion available. Or maybe a monkey or tamarin (Sharn is located in a tropical area, with a rainforest right next to it).
One of the city councilors of Sharn is a shifter druid named Hruit, so there's a contact right there, as is the warforged Smith, cleric of Onatar.
As for visuals, the body of a warforged has not only metal, but also wood and stone. I'd add leaves and tiny branches to the wooden parts and moss all over the stony parts.
I wouldn't make so much as an urban druid, as much as a druid that finds nature even in the heart of civilization.