From the dawn of time, mankind has been making weapons and decorating them for personal use. Initially this was probably a form of identification to prevent theft, but an almost ceremonial use arose around knives, daggers and swords.
As firearms came into existence and were initially made for the wealthy, these same types of craftsmen applied their trade with regard to engraving, carving and the inlay of precious metals.
So it is with the Modern Sporting Rifle to a different degree. The AR15's aluminum receiver may not lend itself to engraving or gold filigree, but a number of craftsman are applying those same principles in the form of "Tactical Bling".
For some it is literally applying precious and semi-precious metals to the art form, others use industrial plastics with laser engraving or injection molding to make their statement.
Steel Flame of Los Angeles , California, makes the most expensive of these with their Rail Skulls and Rear Take Down Pivot pins made of silver or bronze.
Gotham Marketing Group takes a different approach using plastics in the form of Forward Assist Caps.
A cottage industry has opened on Ebay with other vendors offering engraved parts as well.
Whether you just want to add a pistol grip or go all out with Steel Flame's silver, there's something for everyone to personalize their AR-15 beyond scopes and slings.