You should be able to click on it, see it larger and save it to your computer. Then just upload it into your header slot. Or I guess you can link it to the image url. Whatever. Just do whatever you want. Go ahead. Do it.
Also, you wanna know a cool place to hang out with the kids online?
It's especially awesome now that it's all Christmas-y. And my kids really like the games in the Kids Club. (If I weren't hogging the computer all the time, they'd actually get to play them more often like they want to.)