Hi. Welcome to CnH.
Archie certainly is a cutie.
The scratching could be from a number of things. The first thing I'm thinking about is dry skin. The sooner you can change the shavings over to fleece the better. The little flecks of aspen could be getting on his skin (imagine living amidst super-small sawdust particles all day every day) and causing an issue. Also, if there does happen to be a mite situation (the ball on end of quill isn't 100% definitive), shavings can harbor mites.
You really don't have to get terribly fancy with the fleece -- if you happen to have an old fleece blanket that no one will miss, go ahead wash that (unscented detergent; no fabric softener) and cut that to a size that will fit his cage. Or if you can get out to a fabric store and find some fleece remnants/scraps from other projects, that would work well too.
You could give him an oatmeal bath too. Either put regular oatmeal in a sock and swish that around in the water until the water is kind of murky or get some colloidal oatmeal and pop that in the water. Nice warm water (not hot), keep your hand in there so he can climb up if scared, and have a bath blankie/towel near by to dry him off. Just an inch of water max and use your hand or a little cup to pour water over his back (keep it off his face and away from his ears). Just pat dry and let him snuggle in the towel on your lap until he's dry (this will take awhile, so plan accordingly). Do not use a hairdryer; do not rub. And don't over-bathe. For hedgies, less is more. If you bathe frequently, even when using the oatmeal, their skin dries out and it makes the situation worse.
Sounds like you know that major warning signs of a bigger problem include a lot of quills falling out to the point where you're noticing bare patches or an overall thinning of the quill coat. If either of those happen, get the the vet ASAP. If the vet recommends treatment for mites, Revolution is okay; Ivomec/Ivermectin is NOT.
The next in line of possibilities is mites. There's the possibility of stress quilling (though that seems to be more with quill loss alone... not the scratching). Then there are bacterial, viral, or fungal infections of the skin. He could also have an underlying health condition that's manifesting as quill loss (like a URI or UTI) -- we're getting into less and less likely possibilities if the only problem is scratching and a bit of quill loss, but I want to put those out there.
Soooo.... long story short, if the only thing that's going on right now is scratching and a little quill loss, then let's go with "dry skin" as our hypothesis: get him off the aspen and onto fleece and give him a nice oatmeal bath.
Meanwhile, keep your eye on things:
- look at his skin - is it flaky? are there any spots where it's irritated/roughed up/scabby?
- how is his weight - is he gaining? losing? staying the same?
- when you look at him from the top and he's just standing about, how do his sides look - straight from hip to hip? bowed out like an oval? a circle? are his sides sunken in like an hourglass? is he shaped like a teardrop with a bigger hiney than front end?
- how's he eating - what foods is he on? how much does he eat per night?