Since I'm far too cheap to spend money buying pretty stationary (I know, I know, I'm a total immigrant) I usually decorate the paper by hand before sending it off. Like this one, which was made for The Missive Maven, whom I know likes bats:
The first page was decorated with bats; the second one was mostly blank (hey, I only have so much energy) with the odd doodle of a horseshoe crab here and there. When you work at a beach educating kids about the endangered horseshoe crab, and handle the creatures on a regular basis, they start to endear themselves to you. No, seriously. It's reached the point where I think that they are quite adorable. Like this one here:
Awww. See? Cute!
Oooh, and this is neat: The pirate-themed stationary which I made a while back was featured on The Missive Maven in this entry. Sweet!