This first one is really not much of a CAS style, but I wanted to show you that you don't have to make your reverse mask be card front size. Also, this shows how a torn shape can make a very effective look.
This next one is card I made for last year's Dare to Get Dirty celebration at SCS. For this one, I cut out the rectangle free hand, sponged a few greens, and stamped over with leaves and definitions. I went with a rectangle on this one as well. I kept with browns and nature themed images again. So even though each of these card has a more elaborate collaged type look, they come together quite quickly and look really impressive. If you need a gift set for someone, I highly recommend doing something along the lines of the bottom two.