It looks like you've got the plant growing part down pat; everything is so lush and healthy. It's really not a bad layout considering the number of types of plants in there. It's well grouped with different types of leaves and colors contrasting and creating interest. The only thing that bugs me is the front center where the foreground (a moss?) and mid ground plant (E. vesuvius?) are planted across the same width. Any possibility of staggering them so the edges aren't so close together?