It's very good indeed, and a solid proof of concept. I think you've done a great job nailing the brush stroke calligraphic style with the path tool.

I think colouring the river by hand with one of the brushes would work well - at the moment it does look a bit like a bucket fill. Also, the drop shadow/outer glow on the text jars a little with the hand drawn look.

Lovely work - and a very good approach to the problem of city mapping. Have some rep!