Depending on how contemporary you want it to feel, you could go with a white on the walls. Other options would be to use a shade that is in the concrete floors. The darkness of the color would depend on how much light you have in the space so it doesn't wash out!

Right now you have all neutrals so it's wide open for what color to use. As stated white will give you a clean modern look, or you could do varied shades of gray. The last picture shows a warmer color if you like that feel better. When I choose paint I usually start with deciding between a warm or a cool color.

Thanks! I actually saved the top picture. We hope to use some old wood or tin on the property in the kitchen.