I would stay with the marbles, not adding any florals or prints at all. And, in my opinion, beige and/or brown would just look like mud with those brights.
I'd go with the same dark blue as sashing then a narrow border of the light blue and a wide border of the dark blue again. Another obvious choice is a black marble in one wide border with the dark blue as sashing. The blue will balance the yellow without making it look sickly (or sickening).
I actually like the colors. :oops: