Guadalajara is a province in the centre of Spain, mountanious, dry and with a harsh continental climate, for the most part. Here there's a couple of places known as a whole as the Pueblos Negros, "Black Villages". They're made out of a local variety of slate, used in both walls and roofs of houses, pens and churches. They are distinctively dark, thus their name. I think they could be a perfect source of inspiration for the Dornish Marches and the whole of the Stormlands: defined style, trasition between northern regions (more medieval European) and Dorne (more Iberian/Andalusian), eerie feeling (not needed, but why not).
Location of the Pueblos Negros. Check them in Google Maps, most have some streets in Street View! Some notable ones are Campillejo, Campillo de Ranas, Robleluengo, Majaelrayo, El Espinar, Roblelacasa Zarzuela de Galve or Umbralejo
I hope this helps to define the Stormlands style a little bit more!
I hope this helps to define the Stormlands style a little bit more!