When I first started my Ork collection (seven years ago now? Longer?!) I set myself the challenge of never using the same head more than once on any of the infantry models. It’s a subtle little trick but it really adds to the sense of (small ‘c’) chaos and lack of uniformity in an Ork army, and helps to maintain that general aesthetic of unruliness in the face of unifying elements like a common colour scheme. It’s also very practical to achieve, there are just so many Ork heads available between the 40k and AoS ranges, without even starting on all the third-party companies out there.
Until now I’ve managed to stick to it. This gasmask from Spellcrow though – just too cool not to use twice!