Apparently HBO is scouting desert in Spain for a battle scene, and moved a large battle scene out of Iceland to another location because it kept growing in scale to the point that there weren't enough daylight hours in fall/winter to film the whole thing.
It looks like season 5 is moving firmly into unpublished territory.
http://sevilla.abc.es/sevilla/201407...407012257.html
http://winteriscoming.net/2014/07/03...son-5-filming/