howdy.... I have a significant source of wood chips available to me, both well aged and newish. Is one better than the other in a hugel bed? I would likely use a lot of other deadfall from the woods also.
I would go with the older chips (6+ mo old?) as they should be done "sucking" nitrogen in by then. There is also a much better chance of you getting some nice fungi starts in the pile. Plus what Robert said about shrinkage. Let the new stuff age & use it in a few months.
Remember that you can always continue to amend the berm as time progresses. Starting with the old wood is preferred but you can continue to add the newer stuff to the top like a lasagna garden. Good luck!
I would use the vast majority of those chips as mulch for the top of the bed, you could do a couple little clumps of the old chips in with the wood core to inoculate, but that's all I would do with those. Keep them on the surface and let them breakdown into compost and soil there. If you have any left over mulch the ground around the hugel mound with them. The best stuff for that mound is going to be the dead fall you harvest from the forest floor. I think if you put to much of the chips in the bed you will run into a variety of problems that would just be easier to avoid than mitigate.
There is a lot of surface area when you are dealing with chips vs. logs so there is a much higher incidence on N lock-up. The chips could create an anaerobic layer that could result in a gley effect (people use this technique to seal leaky ponds)where water will not penetrate any further so you lose that benefit, you don't necessarily want that homogenized layer in there. Even the old partially broken down chips are going to break down relatively quickly causing rapid shrinkage in the mound. Just to name a few. There are ways to combat these problems or reduce their effects, but like I said it would probably be easier and more effective just to use the chips for mulch. The chips are a great resource, use them wisely. One other thing you might consider if you don't have access to much in the way of larger pieces of wood would be to use the chips as mulch on a more conventional garden layout, or sheet mulch, or herb spirals, or mandala beds, or keyhole gardens, or..... Hugelkultur isn't necessarily appropriate for every situation. One of the big benefits of hugelkultur is utilizing an otherwise wasted resource in downed branches and rotting logs. You lose that if you have to import a bunch of material to create the bed. That being said, if chips is all you've got and you're dead set on hugelkultur then by all means get after it... something is better than nothing. Just be aware you may not see a lot of the benefits that others are.