The AT-ST is nicely modified.
Your trees are a little barren as mentioned and here's my usual rant on all MOCs
The baseplate needs something in my opinion.
I can't stand baseplates and having one with flowers and trees doesn't cover the fact that it's just a baseplate.
I suggest adding plates in up to 3 layers - that would also allow you to make the ground look more real.
The baseplate has that 'flat' look to it.
Of course the above is only suggestions and it's your MOC
Still I'd call it a great start for an awesome little diorama.
"Keep on truckin'!"