One of the first things you will have to ask yourself is where you will be placing your dining table. A round table curiously seems to draw all elements that surround it towards it, thereby anchoring itself (and the chairs) visually more than a rectangular table would. It also takes up less space.
Dining tables and chairs absolutely need to be proportional with each other, as there's no use in having a low table and tall chairs! For a pared back, organic and very zen installation, Japanese designs can be looked to for inspiration, with tatami mats housing a low table and numerous floor-mounted seats. With back supports in place, comfort AND relaxation will be combined to perfection.