If you want it to look more natural, just take out the marine item(yellow coral) and put a straight black background on the back of the tank. I have a straight black background on my 25 gallon and it really makes the colors of the fish stand out. I perfer live plants but that is a personal choice. I used the fake stuff for years and there are ways to make it look a little more natural. Simuliar plants togather with enough space for your fish to swim. I like the use of the rock. Maybe you could add another smaller one for more of a natural appearance if that is what you want. All in all just have fun with it and make it look the way you want it to so you can enjoy it.
Marinemom