I collect the helms, so the MoS helm was a must-get, but if you are looking for one representation, I highly recommend the bust instead. While the helm is nice, it's missing the "mouth", which is the character's main feature. Really gruesome but cool at the same time.
It should be taken by a digital SLR of at least 7 Megapixels... with 5x optical zoom... I believe... the skill of the photographer also plays a part. Personally I always don't know how to adjust the external lighting to capture the picture in the best angle.