I like the simplicity of the design, and I wouldn't do a background IMO. I find that backgrounds take away from the depth perception of the tank, making the "distance" seem flatter and unappealing to me. To add a bit more intrique to the tank, add a few more plants to the background, staggering them, or a terraced effect (short, light colored plants in front, staggered with tall, dark colored plants in the back), will give the tank a bit more depth and shadowplay.
The slope of the gravel is very dynamic, but does take away from the overall volume of the tank. Perhaps when the water level is topped off, the tank will look "fuller" in volume.
The clay pot does take away from the natural effect. Try creating a cavern out of some more stones. That's just IMO.
I do like the tank.
Don't take anything personally, you did ask.
~~Colesea