Nobody likes a sad, empty sofa. A cushion or two (or five!) is always welcome for snuggling into, and the aesthetic boost your room gets from the extra textures and patterns is the icing on the cake. While there are many different ways to create an eye-pleasing cushion arrangement (and with practice, you can knock 'em all out of the park), here are a few simple tips that I use regularly when styling my clients' homes.
Create a strong base
An easy way to create a strong look is to start with two large-ish matching cushions on each end of your sofa (20"x20" or larger is ideal). These can be a solid color or a print; in the above photo from The Everygirl, a pair of bold black-and-white cushions set the tone for the whole arrangement and create a bit of symmetry for the mix-and-match pillows.
Add another layer
Once you've got your base, go in with another layer in a different fabric and a slightly smaller size. You can use two matching cushions again for a formal look, two that don't match for a more eclectic feel, or just a single coordinating lumbar pillow if you want to call it a day, as Eliza and Kate did above.
Do something weird
I like to include an "odd man out" in any cushion arrangement. Something in a fun color, a weird shape (think round or triangular), or maybe a textured number in faux fur or sequins. Here, a bold pink cross sits amongst black-and-white patterns, standing out and fitting in.
Stick to odd numbers
It's true for cushions (and it's true for almost everything else): odd numbers look more relaxed and natural in an arrangement. I usually go for 5 cushions on an average sofa, or 3 on a smaller one.
Speaking of numbers and balance, it's possible (and if you ask me, ideal) to have a balanced look that isn't symmetrical. Here, the larger cushion on the right balances the two smaller ones on the left by echoing one in the repetitive pattern, and the other in coloring.