A leopard pattern would look quite nice--hey, a lot of guys put it on their motorcyles or car hoods.
It might have been Alcantera (fake suede leather) available from automotive upholstery shops...
Anyway, the idea of using speakerbox cloth might be good, but trying to clean the stuff might be a chore. Then again, if it is in the back of the car, what's the big deal of having the dash done in the same stuff? The Ferrari's that I have seen on the street have almost a leather look to the top of the dash. I'm not sure if it is, but it looks that way.
Other things that take longer but that would look good if done right: carbon fiber, Kevlar or a similar aramid fiber. These products won't split in the sun
Davy