Secret Weapon Miniatures have posted a preview of some 28mm Oni Mask head swaps they will soon be releasing.
From their website:
Inspired by Japanese Oni masks these new head swaps will be available in two sets — 5 heads with helmets and 5 without.
The helmeted heads are fully compatible with both the large and small helmet crests from SWM to help you identify veteran, command and other special units.
Pre-order available in December.