Two little nitpicks have: Firstly, their mouths are a bit too wide -- most people's mouths end at about the middle of their eye. I know you weren't aiming for SUPER realistic here but that still struck me. Secondly, Dirk's left arm looks short, probably 'cause you didn't do much shading around the crook of his elbow to show that it's a little bent (at least, it looks like it'd be a little bent). Other than that, very nice, and very precious! <3 I love these two.
One damn pesterlog and I'm shipping these two like a vintage pirate captain, dammit! All tricorn hat, ridiculous fuckin' feather thing, and everything else that entails!
Crazed rant aside, this is a really nice pic! Emotions are conveyed wonderfully, and lil' Sebby chillin' on Jane's shoulder, not to mention the Karkat and John snowmen in the background, are freaking hilarious!