I submitted a photo where I wear a pasta strainer for my official electronic health insurance card in Germany -- and it got accepted, no questions asked! Always good to get some laughs when I have to go to a doctor.
Head coverings were not allowed, but religious ones were exempt. Oddly enough however, a friend of mine got a photo accepted where he poses with a beer mug (Maßkrug, you know, the typtical bavarian 1l mugs). Maybe because that's a religious symbol as well?