It becomes crystal clear to my how lacking in artistic skills I am whenever I try to decide on a layout. Taking some of the helpful suggestions I tried some new things between bouts of washing and rinsing the tank.
You'll have to imagine the sloping substrate in all these!
I tried most on one 1/3 but didn't like it:
Then I tried grouping them closer and moving more toward the left 1/3:
I put in part of the black sand I'll be using as it was getting hard to visualize without it, then tried the stones partially buried.
Not sure though, the back columns have to be in the back corner for perspective, but I think they are a little close. I dunno.
So then I tried a longer slope and put everything on the left third, making a little slope the front/right using the flat rocks.
That might work, and give me a second focal point on the right for a slim, tall plant. I wish I was better at this. Suggestions and comments appreciated, as always!