Some useful links off here:
http://www.camperinterior.co.uk/html/vw ... stery.html
Alternatively, you can buy fabrics, letherette (vinyl) etc from a fabric shop, John Lewis, etc.
I'm also thinking of doing the same - existing door cards not too bad, but want a nicer, more modern warmer covering than vinyl, so might go for a velour covering.
I read a thread somewhere about how to achieve patterns - lay thin foam between the fabric and the card, cut bits of foam out where you want strips and indents, then stick the whole think down. Some will be flat to the card, and some will be thicker with a soft texture.
That's the theory anyway. Just needs a few contact-adhesive fingerprints all over it to spoil the effect.