As a Finn with a grandfather who fought in WW2, I have tested some maps with the Finns. I like especially MonolithicBacon's maps for them:
(2-4) Karelia Winter. I suggest the Winter map for 2vs2, because people usually think of the Finns fighting during the winter. There is also a summer version of it.
(2-4) Karelia Summer. He has also made a excellent 4vs4 map about the battle of
(6-8) Tali-Ihantala, which I like a lot, because there is plenty of space to make maneuvers with light vehicles and tanks. Relic should include it in 4vs4 automatch.