This is interesting, as I have thought about a similar business. I tink there would definitely be a market for, in particular, coffins suitable for children. Teddy bears, etc. Trouble is, unless the death is anticipated, they have to be made individually at very short notice, and I'm not sure how you would market this. There are so few independent Funeral Directors left, most have bee taken over by the corporates, even if the family names are kept, that you would have to deal with the big boys just to get your product in front of the family. On the other hand, once you had them on board you would be in lots of parlours in one go.
I thought of papier mache as a material for sculpting. You could make an entire coffin (wooden board underneath, of courpse) or just a piece to sit on top of a standard coffin.
As a society, we are very reluctant to talk about death. But I've been to more funerals in the last 18 months than in the rest of my life put together. I hope my funeral is a right good laugh. What a pity that we, as a largely post-christian society, so often see death as failure, instead of an opportunity to celebrate a life. I think I'll start saving for a party now!
Cheers
Steve