On many birthing shows I've seen men have a bit of an active role when it comes to the labour and delivery process.
One of them is to hold up your leg/foot as you won't be focused on keeping them up at the time and allowing you to push better. Another is just plain reassurance, letting you know you'll be alright, taking a wet cloth to your head.
Sometimes it seems like the women's partners are the only thing keeping them any sort of "calm" throughout the process.
I'm sure if your DH wants to he'll be able to sneak a peak every now and again to see how the baby is progressing, many men get quite excited when they're able to see the baby at last.
You can have him do you count for you (1,2,3...etc) and encourage you to continue pushing, no matter how much it hurts.
And lastly, he gets to cut the cord! Though their role obviously isn't as active as ours, it's still necessary

we need them!
And because you are doing it naturally like myself, having that little extra reassurance will mean the world I think.