On 6th March 2012 I published an article about the shash (شاش) - the headgear of the Chaldean catholic clergy.
You can read it here.
A very interested article was published on the baghdadhope blog on 29th January 2012:
The Philippi headwear collection is currently the world’s largest collection of clerical, ecclesiastical and religious head coverings and is unique in both its scope and size. You will find examples of headgear from every religious persuasion around the globe, whether ceremonial or worn as part of everyday life. In addition, the collection includes 116 religious objects.