Hi there,
First time posting on this forum.
The map is lovely. Nehwon has been my game-world of choice for many years. Your map, like many on the Internet (and some printed versions) contains a number of 'trap-streets' -- features from my RPG campaign which made it into my versions of the Nehwon maps and were subsequently duplicated. These features, never mentioned by Leiber are:
+ The island and town of Vil-Ning, in the Inner Sea
+ The Land of Mnar, the ruins of Sarnath, south of the Sea of Monsters (relocates from an H.P. Lovecraft story, I believe)
+ The town of Kadesh, and the 'Old Coast' south of Ilthmar
+ The cities of Kartishla and Irilian (Kartishla was mentioned by Leiber but never exactly located in Nehwon)

On the southern Lankhmar Continent:
+ The Isles of Caliphas
+ The City of Carse
+ The Land of Berghof
+ The Forest of Sibilan
+ Whispering Plain
+ The Isle of Xenophon
+ The Isle of Zecy

(I added a few small islets here and there around the coast too).
I guess my maps have been out there long enough to have become canonical, though they are not. There have been very few published maps of Nehwon, very sparse in detail in some areas.

http://quest-bird.com/nehwon/nehw-maps.html