The first, and easiest, technique so to use all those pretty printed backing sheets as cards. Simply trim down any pretty patterns into 3x4 or 6x4 cards. Most packaging is designed to easily be able to trim off the product details, leaving a pretty patterned card for you to use! It does pay to test out different ink before stamping directly onto them as they sometimes have a slick surface.
Another trick is to use the glassine bags that hold lots of bits and pieces in kits as pockets to hold hidden journalling. Just slip a tag with your journalling on it into the bag and add a photo on top. You can also cut them up and use them as layers in your pages.
I find off-cuts of clear packaging perfect for working out your stamp placement before committing to stamping directly onto photos. I use Staz-on ink and carefully stamp onto the packaging and then I can move the stamp around the photo to find the perfect place for it. This is also great to see the placement of a certain sticker or embellishment before placing them down.
And, of course, clear plastic packaging works great for creating shaker pockets filled with sequins or glitter or confetti. You can use a Fuse tool (pays to do a little test patch first, packaging will fuse much quicker than normal page protectors) or stitch them shut with a sewing machine or hand-stitching.
I created a cellophane ribbon ruffle with my packaging and created some sparkly, subtle texture on my title card. Imagine a whole page covered with this sparkly ruffle, so pretty!