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!
While upholstered seats might sound a little traditional or old fashioned, they are actually just exceptionally classic, elegant and beautiful. To modernise traditional dining chairs, grey fabric is a very on-trend choice that will never date or look anything other than sumptuous and stylish. For a really luxurious choice, deep velvets and stunning brocades should be at the top of the potential fabrics list.