Etsy has great options for pillow covers. You’ll want inserts 1” smaller than the covers to make them look plump. Amazon sells some decent down ones, made in the US.

So I always do accessories in groups of odd numbers. It's more calming to the eye. You might want a couple of different size pillows - maybe throw pillows on either end and a lumbar pillow in the middle, or something like that.

Check out Jonathan Adler for what you're looking for.

My couch is off white in color and looking for jewel tone throw pillows, green, blue orange, purple. Not necessarily all those color, could be a combo of 2 or more. I am not sure how to attach a photo.

I would like the pillows to go across the length of the couch. Not sure what size pillows would look best, solid, pattern etc.

Willing to spend a bit more for good quality pillows.