1. Blockchain based new games for gambling platform
2. Decentralized trading platforms
3. Probability of confirmation checker for bitcoin transactions so that bitcoin transactions can be accepted instantly.
4. Decentralized storage
Are few ideas which still need to be developed and this have demand in the market.
1. Lol, why is it good idea? What pros in this idea against ordinary gambling sites?
2. Already exists. But they are not popular, 'cause they more hard to use than centralized exhangers.
3. It's easy to say, but very hard to do. Please, check some technical information before write such ideas.
4. Already exists, lol. Bitcoin Core, Electrum and others.
If in 4 point you mean "storage" like cloud storages, but decentralized that means you're real humster
Such storage will be useless because it will be too uncomfortably to use it.
From that i can say you didn't read any technical bitcoin information and how says in my country - "You say for saying, not for sense"