Complete the look of your sofa or sectional with pillows and throws! Choosing the right pillows and throws to use depends on what you like and how it would work with what you already have in that space. For example my living room rug is multi-colored with muted blues, greens and orange; so I always have to consider what other colors I chose. I currently have (on our old brown microfiber sofa) two pale green velvet 20" pillows and one lumbar pillow with a paisley pattern in muted colors like pinks, orange, blue and green. Then two throw blankets to keep warm, a faux fur ivory throw and a textured yellow striped throw. It's definitely a mix of Winter and Spring right now but all the colors work together well.
You may want to load up your sofa with pillows and layers of throw blankets for a lush and cozy look. Maybe you decide to keep it modern and simple with only a few pillows. Either way is fine and can look great as long as everything complements each other. A sheepskin throw on a leather sofa with textured ivory pillows, will all complement each other well. On a white sofa dress it up with patterned pillows and colored knit throws. On a busy sofa use solid colors or simple patterns like stripes keep and the colors in the same tones.
Keep it casual by mixing it up with different patterns, some patterns more bold and some more subtle. Use odd numbers as your base for how many pillows to use, typically I would start with 3 and then go up by twos depending on your sofa size and style. For a more fun and playful look mix and match different patterns like stripes & plaid, florals & polkadots, paisleys & gingham and etc. Or even mix it up with different textures like furs, leathers, basketweave, velvet, silk etc. A mixed- matched look fits more the styles of eclectic, bohemian, vintage and even farmhouse. Where as traditional styles go for a symmetrical look, modern styles may vary but tend to keep it simple as do minimalist. Modern styles can mix bold colors where minimalist use more neutrals and add interest with different textures.
If you like to switch it up every season, I would recommend getting a few neutral and a few bold colored solid pillows (they can have texture just limit the pattern) as your base pillows that will go with a lot of different colors. If you choose colors and and prints in the same tones and styles they will coordinate with each other easily and make adding in one new pillow an easy update! Or for an easier switch use the same pillows all year but switch out your throw blanket, using heavier ones in the Winter and lighter throws in the Summer. Also pillows with removable covers are ideal to switch them up (and for easier washing) as many stuffed pillows will quickly fill a spare closet but just a bunch of extra pillow covers take up much less space; and will save you money in the long run! I always recommend down filled pillow inserts (you can find some that are non-allergenic) because no matter how many years you've had the pillow it will still be able to fluff back up and look brand new and full again!
Here's some inspiration of beautiful sofas with a mixture of pillows and throws in different colors, patterns and textures!