Not to hijack Rusty Marlin's thread on his fine looking Ruger MKI, but to offer more inspiration in handgun modification, I thought I would mention Hamilton Bowen. A look through his site, particularly the Projects and Gallery headers will show some of his work.
I also can recommend his book, The Custom Revolver, it is more than a coffee table book of his work as it offers his thoughts on design and details in the customizing of handguns. While he does offer engraving and other options, most of his work is in the basic design of the gun, and he stays with the classical lines rather than Darth Vader gizmos. There is some general machining content and plenty if tips and ideas.
The book is well written and organized and includes many excellent photos of details and finished guns.