But how do we know how important they are, or more importantly when they've fallen off? In mass wargames, who cares? In skirmish games many might, and in tactical roleplay it could be critical, not least because there could be things under them. But where's the rule, or rather that option?
And what about wigs, bandannas or weirder, grimdarkling-ish things? The navigators of 40K have a third eye with an effect that in D&D and related games could be save or die: if it slips, we really need to know. They might be the season's must-have accessory - or not - and affect reactions. Here's a simple approach:
A modish hat, peruke, bandanna, scarf or similar confers a +1 bonus for confidence, to either charisma or the equivalent, or to HP or similar if you think that's part of what the total reflects. If no one knows what's modish in a place, any real modifier is 1d3-2, i.e. -1 to +1, presumably kept secret. Fumble an attack in melee, or get a critical against an opponent, strike successfully aiming at the item only or pull off a sleight of hand or similar, and an unfixed piece of headgear falls off, a fixed piece on a further 1 in 6. With each burst of speed or tumble there's a 1 in 6 chance of a fixed falling off, a 1 in 3 in the case of an unfixed, and a 1 in 2 if there's no hand free to hold it. Replacing it, if it's in reach, takes a round.
How's that? Easily exploited for no little chaos in those crazy spur-of-the-moment plans.
If you're interested, the sculpture in the image is 'Listening to History' by Bill Woodrow, and now more than ever you really might want to read the book the cover of which it graces - Czesław Miłosz's The Captive Mind._