So I really like this piece of driftwood but I, personally, am not a huge fan of the straight trunk in most cases. It seems to me that there is a huge amount of interest in the bottom portion of the wood and not really much near the top. I also really like the idea of raising the substrate pretty high in the back left corner and then bringing that down as you go left to right and front to back. I put together a little mock up for you to see that things can be done in all kinds of ways.
Now, being that it is dificult to get good perspective from a pic it may not work this way but you can always cut off branches and use them as you did the blue dotted ones in the orignal. This way it looks like a large tree fell over into a lake and the roots are sticking up. Also, if that large side branch is long enough. you can have it sticking up and out of the aquarium which is a cool look.
Thank, using small buces and anubias on the rocks you can break up the big stump or hide the cut section. Just ideas to make sure you look at things from all angles when creating an aquascape!! Good luck and just remember to be happy with what you come up with in the end.