You should probably limit your plants to the bluish ones and remove the lusher green ones. I'd be tempted to dispense with everything except the bluish bush and possibly the mushrooms, but you should try to avoid overusing any particular tile so it'd be better to either get more variety that fit the frozen environment or have a barren, plantless environment.
As for varying the height of your cliffs, I've got a couple of examples for you:
[1] Really tall cliffs; pretty good from the front but I didn't do a very good job on the sides.
[2] Short cliffs; good all around, in my unbiased opinion
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The key here is that the ledges don't ever last the full length of the cliff except for intentional plateaus. In your case, the only intentional plateau should be the "ceiling" tile and all the rest should either be straight up or with a variety of short ledges like this.
Of course, I did those maps because I like drawing those complicated cliff patterns. The second one was purely for the fun of it. If you don't think it's fun it might not be worth it.
If you want to make things shiny, there are a couple ways to do that. First is by a screen tone that enhances the contrast. Second is by placing parallel process events around the map that wait a little while, then play a small sparkle animation, and repeat (it will do that automatically unless you use switches to prevent it); make sure the wait times are offset among these events. You could also use an icy textured "fog" to add sparkly detail if you like the way it looks.