One of my friends had his 50th recently, and I made a grungy steampunk card for the occasion with metallic inks, aged patina paint, copper layering papers and an awesome large stamp called Mister Bright Ideas by Darkroom Door.
Inside I used the same elements, and added a strip of metallic foil down the right side as well as shadowed gears.
The envelope carried the shadowed gear images and the patina dimensional gear.