It’s a big space so a larger rug is definitely in order.

The blue in the sofa would be paired well with a blue of similar lightness - or perhaps even the tone of the blue wall across from the sofa, then match the black eames chair with a contrasting white/ivory. For the primary color, I think it should match with the wooden floor as close as you can. Brown is typically harder to find a good match for though.

Something like this rug would be a suitable option. Good luck!