I think that stumpy piece on the left is pretty cool. I would try to make that the centerpiece by moving it slightly more to the center and removing the piece on the right. Then I would add some more fluorite around the stump to make it look more natural and use the river stone as accents around it.
I would also change up the background. Graphic backgrounds take away from your plants by distracting your eye. The best way in my opinion is just to paint it as I hate the shiny black backgrounds you can tape on the back.