I think you could go in two different ways: either choose another complementary neutral shade, or something bold that will create a striking contrast. Combining the light cream with a warm beige or taupe would look quite elegant, a bit like coffee with cream. For a bolder shade, you might consider forest green, a deep red, chocolate brown, or navy. Personally, I would choose something in the middle, perhaps a rich slate blue — neutral enough to look classic, but it would great a nice contrast with the off-white.

According to me green is a good color. As you already have opted for mint green then there is no problem in that but if you would like to try cool green then that is also a good option. Actually cool green is a bit lighter one and so the intensity of light is also very good in the interior. You have one more option for cool blue also and it is very soothing to eyes. I would say that just try these two colors and select the best one.