I guess when your Son is in his 20's and an avid car mechanic the obvious choice would be a steam punk card.
As you can see I used real screws ans nuts and bolts from the garage to embellish, with good effect I think.
The card is a box window frame card with good old acetate for the window.
The lady inside is decoupaged to add extra dimension and cogs inside are built up to a 3D effect. This is such a versatile style and in fact can take days to make.
Any comments welcome thank you.