Before the expansion, and while playing it, I always imagined what lay beyond the mountains to the south of ebonhawk, and what the crystal desert looked like. Mainly in my mind was the open sandunes of large deserts. I know that guild wars maps, and open world maps in general, are meant to be more or less abstract representations of a larger world, but that being said I still feel as though we never got that open dune field all good deserts have.
I'm not advocating for some bland, featureless, undulating textured surface for a map, and I've spent some time thinking about various ways it could work. There are a few spots in the current PoF maps resembling deserts in the classical sense, and anet have dotted small terrain assets and mobs between the dunes, so that at first glance you see a desert, and then it delves into more interesting features when you travel through it.
There's also the possibility of taking a multilayered approach, by saying that leylines or sand worms or both run underneath the area and a vast network of tunnels criss cross the area, creating some crevasses and sinkholes in the desert above.
I'd also like to bring some thought to some of the unique ways such a map could be used. The map could have two settlements, one at either end, and an escort mission between them. the mission would take an ingame day or even multiple, the mother of all escort missions across a massive desert. at the end, players are given between 1 and 10 gold depending on how long they escorted the caravan. There's also the potential for rollerbeetle traversal and races and adventures, speeding back and forth across the plains and off dunes with wide degrees of freedom.
all in all, I think that these kind of maps have their place, even in casual games like guild wars and that anet should experiment more with different map 'genres.'