The 1 liter soda bottles and half gallon milk jugs work really well as individual WS containers... they are narrow but tall, so you can put 5-6 inches of potting mix into them and still have some "head room." I've tried using a translucent "sterlite" type storage box (holes in the bottom and in the lid) to hold a bunch of pots with winter sown seeds, but that just doesn't seem to work very well for me, and I don't know why.
