custom door panel?

if you want something that's more contoured, you could always use dynamat or anything with a little thickness to it with an adhesive back (then again, even without an adhesive back you could always use double sided tape)

that way you can apply an embossed effect to any curved surface such as something you have fiberglassed, and then vinyl or carpet over it. one thing that's good for achieving more definition out of the edges is to use a 90 degree hook tool and roll the curve over the vinyl you've applied on top of your piece. also a heat gun is useful (keep in mind too much heat will melt vinyl).