#AmReading therefore #AmEditing in my head . . .
It's not a rule, but a nicety: Place the longest item in a series at the end of the list. This is especially helpful if that item is a prepositional phrase and the others are not. Putting that last keeps readers from incorrectly parsing the list and having to back up to reread.
". . . reams of wallpapers, carpets, paint pots, and scaffolding"
"Reams" applies only to the wallpapers, but at the head of a list it's easy to want it to apply to everything. When that doesn't work, we start over to reach the correct sense.
". . . carpets, paint pots, scaffolding, and reams of wallpapers."
One could go whole hog and make every item parallel by turning each into a noun followed by a prepositional phrase, but it's not needed, IMO. It's already a list of nouns. In fiction there's far more leeway for ignoring guidelines and bending and breaking rules.
One of the important ones, though, is "Don't make the reader work harder than necessary." You want them immersed, not constantly backing up to reread.
#GUMmyStuff