If you are sending a package to arrive before Christmas, you could include some holiday decorations. Strings of lights, a cheesy little light-up tree, some garland, anything that could be pinned or taped on a wall.
I just got a request from my brother for Christmas paper plates and cups--I think he's planning a Christmas party for the people he's responsible for.
When my other brother was in Iraq, I sent him a whiffle ball and bat and that seemed to be really popular.
Don't worry too much about what you send. The impression I get is that a lot of packages get shared. And if there's anything your DH's friend doesn't like, he'll give it away to someone who wants/needs it. My brother is single and apparently gets lots of care packages from single female friends back home. When he gets too much, he gives some to the chaplains to distribute. Nothing you send is going to go to waste.