While we're sharing, I found a few which could represent each of the key centers.

Corevial Castle
[img]http://pre10.deviantart.net/63f5/th/pre/f/2013/144/f/6/the_imperial_city_by_reneaigner-d66drwj.jpg[/img]

Mount Promonon
[img]http://img08.deviantart.net/f823/i/2012/309/c/5/hillside_stronghold_by_andrewryanart-d5j3daf.jpg[/img]

Serpent's Roost
[img]http://img15.deviantart.net/a454/i/2014/180/7/d/casterly_rock__house_lannister__by_andrewryanart-d7fooud.jpg[/img]