My art teacher in high school used to always repeat "look at your negative space" or "be aware of the negative space" when we were sketching a still life or working on a portrait that I now naturally look at negative space shapes everyday out of habit. That habit came in handy when I was working on the previous post E2C Get Well Soon card and I needed a small heart. My mind jumped to this Martha Stewart All Around the Page Loops Heart punch set that my Mom just gave me this past weekend. As you can see in the photo below, you get a bunch of tiny hearts from the negative space that would normally end up in the trash.
I have actually used the waste paper or the "negative images" from border punches several times and I figured it was a useful tip that I would put out there for you.
The heart I used on my card was the larger heart from the corner punch.