The Predators' masks are not cosmetical accessories, they are specialized pieces of hunting equipment, which can prove invaluable during a dangerous hunt.
The mask itself is quite a durable piece of equipment. Made from an unknown metal, it is capable of deflecting bullets & resisting most other attacks with ease. As well as providing physical protection, the mask contains a compact-refractive lense, which allows hunters to view the environment through different light spectrums, effectively allowing them to see in almost any visual conditions, as well as identifying & targeting potential prey with ease.
The mask also contains a compact recorder & directional microphone, which allows a Predator to record the vocal patterns of it's prey, or specific words & sentences which it may hear during a hunt, & project them with the microphone to confuse or startle it's prey. This equipment can also used for communication purposes.
One of it's most important & useful features is it's built-in control system. Utilising this, a Predator can operate much of it's equipment through the mask alone. Small, mandible-operated controls inside the jaw structure of the mask enable a hunter to control the functions of it's cloak, & plasmacaster, amongst other things, without having to touch it's wrist-gauntlet controls, greatly reducing it's vulnerability while using it's equipment.
The mask also provides oxygen to a Predator in situations where it would normally be difficult or impossible to breathe. Effectively acting as an inhaler, although on a much more subtle level. Mounted in the corner of the mask, above the eyepiece, sits the trademark tri-beam laser sight. Once it has identified a target, a triangular crosshair appears on the Predator's internal HUD (heads-up-display), allowing it to lock it's plasmacaster onto a target, & kill with increased efficiency & accuracy.
On top of all the technological advantages it provides during a hunt, a Predator's mask can also signify it's kills, & ranking amongst it's clan. Honoured hunters typically brandish carvings along the crown of their mask, signifying the more impressive of their kills. The blooding mark is also burned onto the forehead of the mask upon a young hunter's first Xenomorph kill, for the clans that perform the ritual.