So we know that a maps location is based on the first time you look at it, but can you craft a map of the Nether?
Yes, but they don't do you much good. From the wiki:
While maps in the Nether work, it has a ceiling, and all that will be shown is red and gray. The only useful function is finding where you are in relation to where you made the map. Additionally, the direction indicator rapidly spins and is not a good indicator of direction. Remembering that maps are East at the top and that the L corner of nether blocks points north is more reliable. And as long as the map was created near a portal, that map's center will always be that portal.