In this picture you can see the cream colored cashmere pillows I have had for about a decade that now have various holes on the back side, how they got there I don't know. I'm just going to blame the cats. The front side was a nice cable knit cashmere, but there were a couple of tiny holes in the front, but with kids when do the pillows ever stay facing the right way so company doesn't see the holes on the back side.
This was a simple enough project with minimal sewing skills needed. My daughter & I picked out fabric from JoAnn's that was in their home interior section (thicker & more heavy duty fabric in this section) that was in their discounted pile of bolts. A yard of this fabric was $6 and was almost exactly what I needed, there is minimal scraps leftover.
All I did was simply sew along three sides with the wrong sides facing out and then turned it right side out, folded in the fourth side and pinned it and stitched that down in a coordinating color of thread (which I was lucky enough to have some.)
Six Dollars! That's it! For 2 new pillows. And nothing is going in the landfill because I kept the cashmere cases on them so that it provided a smoother look.
But if sewing is not something you are interested in doing, check out buying pillow cases from a store to give your pillows a new look (or in my case get rid of the used-up look). Stop yourself from throwing away a perfectly good pillow when it just needs some updating.