Based on service of Icelandair you may consider to book some interesting fares to Seattle in America with an optional stop-over in Iceland during winter season 2015/2016. Rountrip flights are now available already for €354 when departing from Scandinavia (Oslo is the cheapest option). You have also an option to book open-jaw ticket and return back to Germany (Frankfurt, Munich) or UK (London, Manchester, Glasgow) already for €411 or £275.. You may also consider multi-city flights from UK to Iceland and Seattle at once already for £320..
if interested in this deal you may find the cheapest flights to America with possible stop-over in Iceland at the end of November and beginning of December 2015. or between 12th of January till end of March 2016 (Date of your outbound flight to USA). The easiest way to check your connection possibilities is through Skyscanner. This tool gives you quickly a rough idea which low-cost airlines are connecting your home town.
Another interesting promo deals with Icelandair are multi/city flights from UK, Amsterdam or Scandinavia to Denver and Iceland would cost you just £342/€392. Last but not least is attractive option to New York, one of the most demanding destinations with possible stop over in Iceland already for £299/€359.
Booking samples
Currently valid promo codes (accommodation)
Booking sample of cheap flights to USA (Seattle) + Iceland from Europe at once from £275/€35 here. In this case you would be flying from Oslo to Seattle on 27th of February 2016. Your return flight from America back to London would be on 12th of March 2016.