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.
It's a commonly accepted myth that dining table and chairs have to all match absolutely perfectly, but a little variation can work terrifically well. By selecting a few different shades for seat pads, a funky and modern look can be effortlessly created and against a neutral backdrop, such as a white wall, the visual impact will be utterly incredible. Different colour palettes could even be used, seasonally.