The gravel has gotta go.
Even what you have however you can work with, first thing I'd do is lose the symetry, it's boring. Instead of putting something in the middle, two plants on each side with a small plant between them, try grouping them together. Maybe put all the tall plants on the left two thirds of the tank, and the centerpiece slightly to the right of center. It will increase the thickness of your planted area and it will also give your tank more variety by having an open area and a planted area. Move some things to the front too, obviously not the tall plants, but maybe move your centerpiece to the front of the tank with plants in behind it, having every little thing stuffed in the back is also boring.
Lighting also helps alot, proper lighting can make an uninteresting tank look very nice, and have the opposite on a really nice tank that is left unlit. Definately get those lights on a timer for a few hours a day.