I'm working on some little gift bag ideas right now, and I'm trying to keep it simple, but of course a little bit cute! Anyway, not sure if I'm quite there yet, but I have a ton of white lunch bags so I came up with this idea (not a new idea!). You can use any size lunch bag - they do vary - and just measure your cardstock the same width as the bag. Then you cut down the bag to however tall you want it (mine here is 6" wide by 6" high - perfect for 12" x 12" cardstock). So, you cut a piece of cardstock 6" x 6" to cover the fron of the bag. Then you cut a piece a little longer, 6" x 8 1/4" and score it at 6". This longer piece creates a back cover. Then you can cover with Designer Series Paper (Cottage Wall here - LOVE it!!), and whatever else you like!
Hope you're having a good week!