Suggestions for future and much later updates:
1) Underwater exploration. You can collect different materials instead of the ones floating around, and the shark/other creatures can be a threat
2) Instead of islands (because the whole concept is to survive on a raft), why not have broken down boats/other rafts deserted in the sea?
3) Maybe some other decorations like a sail, flag, or a small plant
4) Possibly other threats to damage your raft in different ways? Like a storm or other animals out in the water. They can take more parts of your raft or only one object (Like walls)
As a side note I want to say thanks for making this game! The concept of surviving on a raft is pretty neat and I like the gameplay so far. I hope you guys don't rush or over work on the game, we can always wait :D