Wow that's nice! I just thought of something that might have been a tad late but whatever. You could get some small sticks that look like trees, or make a copper wire tree, and then cover it with christmas tree moss and scatter it around the background. Also I think you should add more plants or add some floaters as it looks too bright.
EDIT: Actually you could just put Christmas Tree moss on the rocks.
Like with all my other tanks/bowl/Jars i tend to add plants in along the way. I'll let it all grow out and then replant trimmings to fill it out.
I've also already attached moss onto the rocks at the back!
Floaters i will add at some stage too.
Still got a fair bit of room for more plants.