When I moved into my current apartment I wanted to go with an all-white European rustic theme for my bed. I had already made pillow slips out of heavy, linen-look rayon for my "sleeping" pillows, but wanted some throw cushions to match.
IKEA carries very inexpensive feather cushions, and I made slip-on covers for them out of vintage fabrics from my stash: two old 100% linen tablecloths, an old, worn 100% cotton sheet (lined with more cotton since the sheet had holes in some places), and 100% cotton muslin.
Each cover has a slit in the back (I don't like zippers on cushions) so it can be removed for cleaning. They look great on my bed, giving it the feel of a European farmhouse.