The terrain looks pretty good so far, but there are some thing I would add.
One thing I really like to do is mix terrain. What I mean by that is to use different terrain in the same area to “mix” it. This can give your terrain a realistic feel if thats what you’re looking for. You can also can do is use the grow and erode tools to make any flat places in your terrain uneven. This also helps create a realistic look.
I see that you’re already adding vegetation, which is good. Trees usually take a while to make by hand, let alone building a whole bunch of them to span the entire map. Fortunately, you can use this plugin helps to quickly create customize-able trees.
Yeah, going along with what @DasBaum2 said, Terrain Editor isn’t the best thing for me, you’re better off getting a plugin which can possibly look better and can make the job easier.
Well, if I’m going to be honest, the terrain looks very bland. I don’t really understand why you just scattered lava everywhere, it makes it look like blobs of salt on a plate. What I would suggest you do is, make the lava look more connected or compacted together, it would give a better look. I hope I wasn’t harsh, looking forward to your work!
Looks good but it seems the terrain jumps from one type to another, try playing around and making it fade/mesh to another. Like a cliff should have a bit of dirt, grass, and rock. Think of real life and the mashup it is, and how everything flows into eachother and parts are exposed.