There are an endless number of nordic itineraries. Ultimately, it is up to you what you prefer. However, you should include the following destinations per country:
Norway: Oslo (The Vigeland Park, Viking Ship Museum, Frogner Park, Akershus Fortress, Normarka forest, TusenFryd Amusement Park, National Gallery, Akershus Fortress, Nobels Fredssenter, Holemskollen Ski Museum, Norwegian Folk Museum, Oslo Cathedral, City Hall, Royal Palace), Stavanger (Preikestolen, Lysefjord, Norwegian Petroleum Museum, Cathedral, Old Stavanger, Swords in Rock, Sola Strand), Svalbard archipelago (Global Seed Vault, North Pole Expedition Museum, Moffen Walrus, Magdalenefjord, Snowmobile Safari), Trondheim (Nidaro Cathedral, Kristiansten Fortress, Munkholmen, Stiftsgarden), Lofoten Islands, Bergen, Western Fjords, Tromso, Geirangerfjord, Flam, Sognefjord, North Cap, Flamsbana (Waterfall).
Denmark: Copenhagen (Tivoli Gardens, The Little Mermaid, Amalienborg,Nyhavn, Viking Ship Museum, Zoo, Kastelet, Opera Haus, Egeskov Castle, National Museum of Denmark), Arhus, Skagen, Odense, Alborg, Helingor, Roskilde, Herning, Billund, Kolding, Vejle, Frederiksberg, Viborg.
Sweden: Stockholm (Gamla Stan – old town, Storkrkan Cathedral, Royal Palace, Nobel Museum, Skansen Open-Air Museum, Drottningholm Palace, The City Hall, Abba Museum, Nationalmuseum, Gröna Lunds’s Amusement Park), Karlstad, Gothenburg, Malmo, Helsinborg, Karlskrona, Lund, Kinkoping, Umea, Uppsala, Visby, Vasteras, Orebro, Sundsvall, Kosterhavet, Marstrand, Wallander Ystad, Icehotel in Lapland
Finland: Helsinki (Cathedral, Temppeliaukio Church, Market Square, fortified islands of Suomenlinna, island of Seurasaari, Sibelius Monument and Park, Uspensky Cathedral, Lnnanmäki Amusement Park, Kiasma – Museum of Contemporary Art, Railway Station, Ateneum – Finnish National Museum of Art, Finnlandia Hall, Korkeassari Zoo, Kansallismuseo – Finnisch National Museum), Tampere, Rovaniemi, Jyvaskyla, Oulu, Savonlinna, Turku, Rauma, Vaasa, Porvoo, Joensuu, Lappeenranta, Espoo
Iceland: Reykjavik (Modern cathedral, Harpa Concert Hall, Perlan Museum Glacier, Arora Planetarium Show, Mountain Helicopter Tour, National Museum of Iceland, Arbaer Open Air Museum), Hvammstangi, Akureyri, Egilsstadir, Hofn, Vik, Geysir
Faroe Islands: Sorvagur (Vagar Airport), Torsshavn (Capital), Klaksvik, Fuglafjordur, Vestmanna, Hoyvik
Aland Islands: Mariehamn, Finström, Joamala, Lemland.
Greenland: Nuuk, Ilulissat, Sisimiut, Qaqortoq, Aasiaat, Tasiilaq. Maniitsoq.