I've been there twice in recent years, and am planning a winter trip. (Hey, it's a lot warmer in Iceland than South Dakota in winter!) Anyway, the most important thing to bring would be your polarizer. I'm not kidding. As for lenses, anything in the 24mm to 200mm range will do 90% of what you want. If you want to photo puffins, bring a 400mm. For film, I'd suggest a good ISO 100 color (such as Ektar 100) and a few rolls of HP5. When I go back I will take my Nikon digital camera but also a Leica with lenses 28/35/50/90mm. B&W in the Leica, mostly FP4.
Kent in SD