Sorry for putting my five cents in...not interior decorator but do have eye for color, however, not seeing the room is hard.
But black and white posters will call in my opinion only for a very plain thin silver framing...basically metal strip all around...probably would be nice if it's kinda...has a little curve to it in width instead of being flat.
Not good with measurements but sounds like walls are rather tall and prints are not so much...if that's correct, another suggestion would be...do not hang them in a row...make the middle one lower than the others...and the right one possibly slightly higher than the left...although left and right on the same level will work too...or hang them diagonally period...depends how it looks like.
Otherwise...you can always fly me over???
