This is the pathtag I created for our family with animals that represent us, using our dog's face again, as I did in creating our stamp for letterboxing. We haven't yet found an actual letterbox, but this is a picture of the log from a geocache/letterbox hybrid we found in Massachusetts. Each letterbox has its own stamp image that you collect in your own book. At the same time you create your own stamp and leave that image at the letterbox book.
If you're looking for a new hobby, might I recommend Geocaching.com, Pathtags.com, and letterboxing.org. Just a few more ways to be creative!