Your challenge is to use some type of leftover materials to create a project. And if you really want to challenge yourself even further, you can try to create a non-holiday card from your leftovers.
I made quite a few gift bags using the edgers #3 die, so I had some leftovers from those. I then cut out the crown image from one of our Christmas cards to use on my project. We have quite a few family birthdays coming up soon so I now have a gift bag to use for one of those.