Hey there :3

Firstly, terrain. I like it - you have good diversity with the layers that you've created, and you've managed to create a second level too, I like it. However, the second level looks a little unstable, and I'm going off the assumption that if you had more plot space, you'd expand upon it.
I'd suggest as well, mixing more block types into the soul sand; having the whole thing as one block is a little ordinary to look at - make it more exciting! You can keep with the dark theme by adding brown/black stained clay etc. Play around with it :3

Secondly, organics. You have a good organic in the centre of the build; I like the idea behind this build. I've never seen something like it, but it's good!

Structure, however, is needed on this plot, I think. Normally I wouldn't, but because the organic isn't too difficult of a shape to make, I would like to see some form of structure on this plot. Maybe a hell/nether themed tower on top of the corner cliff? ^.^

Good luck!
- Dutty :3