Back in the 90's I spent a year delivering flowers. I loved the job but I will never forget the day I started. I went out with the guy I was to work for to learn the route. As we drove back into the depot with a van full of beautiful flowers he said "these will all be compost in 3 days. One florist said they used the oldest flowers in their cool room for funerals because people wanted to see the flowers full blown. The cost of casket arrangements was enormous.
I think all the suggestions made here a fabulous. Thankfully I haven't been to many funerals but these suggestions will be kept because my friends & I are not getting any younger. I have always sent potted plants rather than flowers to friends or family if the have been in hospital or needed cheering up. Balloons are another great thing but obviously not for funerals.