I made them all the same size. This time I will make different sizes as the cats could use smaller ones. I didn't take any pictures of them I forgot, but they were about the size of a bed pillow. Now nothing gets thrown away. I put my salvages in there , squaring up blocks, trimming fabric anything. Check out your local pet store. I am sure they would appreciate anything you sew.
The lady in charge told me they even use old baby blankets for cats. Any old blanket that you may even have around the house cut it smaller and sew the edges. They use those for their cages during traveling. The picture is a new case I sewed up this morning to start a new pet bed. Let us not forget these pets.