I own 2 Noj sets in Walnut and Maple, Dubrovnik II and BCE stage 2 with Stainless Steel bases.
I agree about finding a board where there is good contrast between the Black pieces and the dark squares.
With that though, there are some Walnut and Maple boards that are almost perfect with the Walnut sets.
For the BCE I suggest a 2.25" square sized board as that set plays a bit bigger than the Dubrovnik set.
I have a Drueke 2.25" board that has the squares not as dark and it's great.
I also use a standard Green and Buff vinyl board and that looks and works great at tournaments.
I do also use a leather roll up board where the dark squares are a darker Green and the leather of the light squares is a lighter tan. That is actually my favorite set-up.
What would be a good material for a wooden chessboard if the chessmen are made of walnut and maple? I like the traditional walnut and maple chessboards, but I am afraid there would not be enough contrast in this case.
I will soon be receiving a set of Noj BCE stage 1 chessmen in natural walnut and maple and I am especially interested in what other Noj owners are using for their walnut chessmen.