Hi Import,
You can do anything you want to make your cars look good. like Enzo asked, what car, year and all that because every year even the same style of car has subtle changes. I add things like spark plug wires, heater hoses, radiator hose, some folks go as far as doing brake and brake lines. Don't be afraid to try anything new, the only thing that will hold you back is YOU. Just use your imagination and think of what you want to add to your project and go at it.
Hope this helps, let us know what project your working on. I'll help any way I can and I might just learn something from you.
Ken
that which doesn't make us irate or irritated,
has probably been thrown against the wall.