I like Iselin. I think it's a nice alternative to more overused Is- names (
Isabel,
Isabella etc.).
I'd pronounce it EE-zuh-leen, but I have no idea whether that's a legit pronunciation or not. I'd try
Isa or Line/Lina as a nn.
Since you like Norway you could another Norwegian name as a mn:
Iselin
SolveigIselin
AstridIselin
EiraIselin
HildaIselin
Ragnhild
Or you could combine it with something more usual:
Iselin
RebeccaIselin
SophiaIselin
LouiseIselin
Maria