Before you consider anything too contemporary or radical, consider the affect the environment will have on the fish.
Fish are actually very wild by nature. They look for predators, they need places to sleep and hide. They are affected by how much light they get (and what direction they get it from), what colour their gravel is and whether or not they have a background on the tank. Tiny details, but they can make all the difference between healthy fish and stressed, sickly fish.
A few examples:
In nature, most sand in lakes and streams is quite dark. Many fish have adapted to be dark on top and lighter under, in order to camouflage with the sand and sky. Take this away from them by giving them very light (or even white) sand, and they will become stressed.
Many fish also come from dark water, with lots of roots and plants to hide in. Take these fish and out them in a sparsely planted tank with a few "set pieces" (such as pirate ships and arches) and they don't settle or thrive as well as they should.
Many decorations designed to look good are also fairly fish unfriendly. They are rough, or have small holes to get trapped in, or moving parts that crush. Some leak dyes into the water or flake off paint.
In a fish tank you are creating everything the fish need to thrive and be happy. The environment needs to fulfill their needs for safety, darkness, day and night and shelter before it's fulfills yours.
That said, one can be very creative as long as their needs are met.
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