Well to start with....to fit all the tanks I want....I would first need to buy a massively huge house to fit all the fish I want....then I'd get....
1. A huge reef tank setup like that person I am insanely jealous that posted all the pics of his tank (with the room with the blue walls...sorry...can't remember his name...but I will NEVER forget the tank).
2. A huge Mbuna setup...my 75 gall would be small in comparison
3. Many many platy only tanks...males only...females only...babies...etc.
4. An angelfish tank
5. A community tank with peaceful fish
6. A moderately aggressive tank with tiger barbs and the like
Man....I could go on all day!!!