That looks really good; city maps have never been something I'm good at, or can even do :/ as to getting an aged look... no idea! maybe make a layer with the artistic>apply canvas filter, colour it brown, and then put it over the other layers with low opacity? Or, I believe you can find some parchment images somewhere on this site to download... perhaps put your map on top of on, and reduce the opacity?
Anyway, this looks great as an aspiring writer myself I'm always interested to hear about the stories others have planned