Thanks for the suggestions Raymond!
You are right about the level substrate, I gave it a shot after Solcielo mentioned it, and it is not possible with the egg crate. I considered cutting the egg crate back, but then the slope wouldve been extremely steep going towards the back on the right side. And I wanted the wood to escape the top of the tank some, as it is now. So... I'll break the rules and have a sloped front edge :icon_cool
For your suggestion in between the two limbs, I had planned on planting some anubias and maybe a brown crypt in that gap, possibly a little behind the gap so they grow through towards the front. A rock could still work wedged in there, with the plants growing out and around it as well. I may give that a shot!
The nana petite idea is good, I had planned on planting some of Anubias along the upper branches and letting them grow emmersed. Throwing a petite along that branch could be cool too. I have some xmas moss coming for the submerged branches as well.
I appreciate the suggestions a lot! It's nice to get others opinions on these sorts of things. I tend to get tunnel vision after awhile, and a second opinion helps break from that