I took the one of Nathan with the thunder clouds behind him off, as it was over a year old, and also - I'm about to be a mommy to more than one baby (and the chances of me getting a picture of both of them that I like turned into a blog header are pretty slim - at least for a few months). And I kind of like the artsy feel of these pictures (taken by my friend Carrie)..... They won't really outdate as fast as pictures of my quickly growing kids.
So I'll just let the votes decide. Although if my husband decides to voice his opinion, that might trump all votes.