Now thats an improvement, now would be the time to start focusing on details and important stuff.
You should by now start to think about what you personally think looks good. Or at least, what you SHOULD think looks good. Spamming the same tree model at the same size (mostly) in the background seems natural and appealing to you? No? Now start focusing on variety, there is never a forest with only one type of tree, and if there is, then they will be in all sorts of sizes from spall sprouts to large overgrown near death bunks, always have like 2-3 different tree models, or any model for that case, to use.
Variety is something that makes a terrain look good, and using the same kind of doodad over and over again besides one another will look "spammy."
Now, when it comes to doodad placement and camera angle you seem to be quite good now, only thing is that you can use more doodads in some of your terrains, leaving large open empty spots of only tiles doesnt look all too good.
When it comes to background you have something to work on, I can see in your desert terrain that you already know how to use and enable the fog, and you should use it even more. In most cases these settings will be useful:
Z Start: 0
Z End: 4000
And from there and henceforth you can experiment yourself, if you want the fog to be thicker you make the "4000" a smaller number, and if you want it to be thinner then you make it a larger number.
The horizon should never clash with the sky to make that "end of the world" feel, you should use the fog to make the background seem like it is smoothly fading into the distant, dont be afraid of making several layers of mountains in the back of each other to prove this point
Now, thats something to work on, hope it was to some help.
