Very nice to see you're entering the contest
It's good that you start working/posting in the recommended image dimensions.
For the viewers and you it is easy to see what the image has/lacks this way.
Looking forward to see your next iterations.
I hope you don't mind I share some thoughts on how to approach this contest:
I would not start this way, by choosing the vegetation you want to use. I'd first think of what I'd like to make/show and then design a terrain which supports this idea. Then I'd roughly lay out an animated path for the camera. This does not mean you actually have to animate a path, but make one in your mind. Then start detailing your terrain and check how it holds on all 6 frames.
Then if that's all ok I'd start adding objects/populations.
What do you think about this? It's of course a type of workflow, and thus quite personal perhaps.