I created that map in Adobe Illustrator, mostly with the Pencil tool controlled with a Wacom tablet. I had a fairly big advantage with it since I had Mitchell's most excellent oil painting map for reference. The icons were mostly recreated from reference using the Pen tool. I think there were a couple that I swiped from a WoT wiki. The icon for Bandar Eban, for instance.

There's nothing there that you couldn't do just as easily with Inkscape, except the border, which was an Illustrator pattern. You could certainly make something just as good in Inkscape, but it would simply take some time and patience. And maybe Inkscape itself has some similar patterns by now; it's been a while since I looked at it.