I've been looking at the tank and have been trying to picture if the wood would look better oriented differently. Maybe flipped to form an arch, or one end lower and let it climb towards the surface at a corner, or possibly cut it into 2 pieces and add more. Maybe add some large rocks to one end of the wood and scatter a few random pieces along the length?
Any suggestions? Really need some ideas here ,this is a lot harder than it looks to visualize. I've seen the amazing tanks members on here have and I know there is lots of very creative people here. I, myself, am more mechanically inclined, I can see and build just about anything. There is no artist in me.