I wanted some accent pillows on the couch/sofabed, but I knew I wouldn't have any place to store them when the sofabed was in use. I also had guest pillows that needed a place to live when the sofabed was not in use.
As a result, the accent pillows became guest pillows, and the guest pillows became the accent pillows.
I fell in love with the front fabric at Bolt and waited until their big sale before buying it. I didn't want to spend the money to get enough to make full two pillows however, so I got just enough to make pillow fronts. For the back I used far less expensive cotton fabric (flannel for one, just plain quilting cotton for another). The backs are quite simple, no fasteners, and are easy to remove and clean.
I now have a ridiculous number of throw pillows for one small couch.