If you have one formal and one casual dining space, you can really go to town with different chair designs for both. A casual spot will do best with sociable, comfy seating that naturally leads to conversation, whereas a formal setting is where you can play around with luxury fabrics. If you only have one dining room, you're going to need to combine all of these elements in one set of chairs, if possible!
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.