I love my furniture to be classic and with straight lines. The décor of my house stays unchanged like that for a long time. You see that is indeed the advantage of having furniture that is not too contemporary because very soon it starts looking dated. Then you would want to change the décor of the house all over again, maybe do it from scratch. And that could be a costly affair.
On the other hand, if you play around safely with time tested designs, you can easily have the design core for decades without needing to change it comprehensively. You could add a few touches here and there and make sure that you come out with a new look every season or every year.
I love to add touches with colorful splashes across my plain colored walls and furniture. For instance, my chrome yellow walls have a collection of contemporary art pictures with splashes of crazy colors. For the furniture I use colorful and pattern rich durians with hanging tassels to give a glam look. And for the furnishings nothing brings out the magic in them better than throwing colorful cushions on them. You can play around with colors and patterns to give your room a whole new identity each time you have a do at your place or someone is visiting for the second time!
No rules for cushions:
Cushion fabric and pattern greatly determine the look for example you could use silk cushion covers to add the regal touch to your settee. You could throw coarse cotton ones in some color scheme to get a cool casual look and sometimes you can cover them with kitschy covers to add to the chic content of the room. I always look up online stores to get a feel of what is in season. Infact I have bought my favorite cushion fabric for my cushion here only. And let me tell you I never regret!