When you say dragonfish do you mean arowana? I think a dragonfish would suitably live in your tank, i dont nkow, but i think. ah, here i found something about them "You will have continuous problems unless you keep these guys in brackish water. Add two to three teaspoons of salt per gallon. If they start looking slimy, change half their water and double the salt in their water". Moray eels get very long. Most eels prefer brackish water to i believe, they also get very large, Maybe a better alternative would be the rope fish, which looks like an eel or snake but is just a fish. Even rope fish get very large. One reference says rope fish get as long as 60 cm, which converted is around 25 inches.
Black knife fish also get very large, 1'+ i think.
The painted glass fish is a glass catfish with dye injected into its body, they seldom last longer than a fem months in an aquarium. They do the same thing with glass tetras.
If you like colorful fish like that you can get glolight or neon tetras and such, but iw ould avoid the PAINTED glass fish. you can get glass fish which are just fine and healthy.
The stonefish gets between 35-50 cm long. They are also saltwater i believe.
As for sharks:
THe flying fox gets about six inches long, they are peaceful and can be kept with other fish, they can be kept with other flying foxes as long as the tank is big enough for them each to have their own territory, and good news is, they are suitable to your aquarium.
The rainbow shark also gets around six inches but i think its more aggressive and suited toa larger aquarium, you might could make it work though. (someone correct me ifi'm wrong).
I havent had much experience with sharks though.
Eels are aggressive, stonefish eat any fish that fits in their mouths along with snails and crustacions.
Knife fish are semi aggressive (and large).
Glass fish are a go. and a couple different sharks could work.
What type of aquarium are you looking to have? maybe give us some specifics on what your looking for and we could help with some fish suggestions? best of luck buddy.