Okay, first off, I think it looks nice, maybe just a small tweak, but overall a very strong starting point. :)
There are some really basic composition principles when it comes to art, and they apply to just about everything, from room decorating to aquascaping. :)
1. focal point should NOT be in the middle. (which is going to be crazy hard with a corner tank)
2. your eye should flow from one side of the composition to the other, drawn along by lines created within the comp.
3. Typically you have one focal point, but in a larger tank you can have two, typically one on each side.
4. NO matchy-matchy. If everything looks too symmetrical it ends up looking weird and unnatural.
5. No straight lines across the top or bottom. The tank should go up, then down, then up again, or vice versa, low to high to low. This is one place where you can be symmetrical in the LINE, but not the overall look.
6. In the two focal points, you want variety. Do the driftwood as a focal on one side, then make a large beautiful plant the focal on the otherside. You can still use driftwood on both sides, but it should be the focus only on one.
7. Plant types, colors, décor should travel across the tank, don't put all rocks on one side and all driftwood on the other, make sure they are represented across both sides. They don't need to be equally represented (best case scenario is that they're NOT), but have some hints on both sides.
Those are the basic rules...and they can all be broken in the right ways, lol! But, for a beginner these are tried and true, and can help along the way. :) I had enough art classes through my education that these suckers have been drilled in! :)
Also, go on youtube and look up planted tanks. That's where I've always enjoyed looking, those huge professional deals that are *amazing*...On one hand I always feel hopeless because I'm never going to get there (lol!), but on the other side, it gives you a great feel for positioning and 'scaping. :)
I hope that helps! :)