You can be inspired by the French soup bouillabaisse, or some similar (of course you don’t have the same fish). It is one of my favourite fish soup. Maybe you will need to add more fish, the bones are not enough to make the soup tasty enough, it is a full meal on its own.
I have made sauce with shrimps heads, delicious! I guess fish carcass will give excellent result.
I am not an expert in Malaysian cooking, they make good use of fish heads cooked in curry. More about it here.
