1)SYSTEMS AND UNITS OF MEASUREMENT. They have magic. Yet they have no quantitative way of MEASURING magic.... to determine how much of a magical charge an artifact has, or how fast it is draining or recharging, no equivalents to volts, watts, ohms, amps.... seeing as this sort of thing is a matter both of human nature and utility, they should have SOME sort of system for measuring magic, if for no other reason than objectively establishing which wizard was "stronger" without a dueling tournament.
2)This is coattailed by ENERGY CONSERVING DESIGNS. Regardless of how endless or "free" magical energy is, wizards get tired and enchantments run down--- which means there's high motivation to produce designs that are more "fuel efficient." Take brooms: At least one person had to have hit on the notion of attaching a bicycle seat to a broom rather than waste magical juice on a cushioning charm, for example.
3)Expand into general DESIGN PHILOSOPHY, Other than tradition. Regardless of where you start, under the influence of individual need, FORM FOLLOWS FUNCTION. A chair, regardless of culture, needs to be shaped to hold up a butt.....
Continuing with brooms, you don't see equivalents of headlights, navigation lights (port and starboard), luggage and cargo capacity (such as saddlebags), multiple passenger size. Magic carpets have that at least; it would take someone cutting off their nose to spite their own face to outlaw those things. Why not a flying la-z-boy recliner, for comfort?
Magical suits of armor make terrible guards-- what could be less well-thought-out than sending out a warrior to fight who was nothing more than a hollow metal shell? They should at least have an internal load-bearing "skeleton" to put weight behind their blows and enable them to hold up against blows in return without crumpling. There should be separate floos for communicating and traveling--- using the dual system in the book is just begging to be kicked in the face by someone going the other way. in fact using them to communicate should be outdated: Sirius' two-way mirrors should be common as cell phones in the muggle world. Large magic mirrors, rather than a Wizarding Wireless, for entertainment-- and why not 3d tv using illusions cast by the wireless, at that? and so forth.
4)there should be MORE INFLUENCE FROM AND AWARENESS OF THE MUGGLE WORLD. A smaller society that hides within a larger one is going to, by necessity, be more aware of the larger. The Potterverse is the exact opposite: Muggles, from folklore and popular fantasy, have a better overall picture of the wizarding world than wizards do of the muggle world, despite being literally engulfed and surrounded by it. The wizarding world should be awash in Muggle art, music, clothing styles, pop culture, etc. just from the debris and litter the muggle world leaves behind (newspapers, magazines, books, disposable goods...) If anything, the wizarding world should be a mish mash classical folklore and the wildest imaginings of pop culture--- futurism, zeerust, etc.--- because unlike muggles they are not constrained by the limits of engineering or physics or even three-dimensional space. Think either victorian sci fi, Spelljammers... or perhaps even Dr. Who.