The Wave Magazine has an article, Alternative Funeral Resource Guide, that has some interesting alternative ideas to decomposing in a casket:
1. Be shot into space
2. Be turned into a mummy
3. Be frozen
4. Have the casket decompose along with you
5. Be transported in style
6. Be scattered at sea
Here’s some more ideas:
1. Be buried in your furniture
2. Donate body to science
3. Be dissected by medical students
4. Be plastinated