Meetings are more productive when a room is comfortable. Comfortable natural colors are best. A comfortable chair and a comfortable temperature make it easier to have a productive meeting. A rectangular table also is makes people more comfortable as well as a pleasant scent. Especially jasmine or a lemon smell. Who wants a stinky smell. Also good lighting obviously so you can see the others well as well as plants. A high ceiling also makes a meeting more productive because you do not feel trapped in.
Read more: Yes, Your Paint Color Matters: How to Make Your Meetings More Productive