pillow cases -
I purchased some 12x16 inch "little" pillows - and made pillow cases for them - I used the "housewife pillowcase" style
That style might have another name, but that's the name that gave me the "how-to" for making them. (The dimensions given on that web site were for either a queen or king size pillow.)
It's an envelope style and looks quite neat and tidy.