[Crono]

A few pointers:

Don't stack grass over grass everywhere, it doesn't look very good. It's ok to have some consistent grass layering but it has to look good and not be overdone.

Detailing should be more rounded, your detailing is too square and is not very attractive. Detail is one of the main ways your level will be judged in terms of how nice it looks, so it's important to fix such styles.

The third screenshot has a lot of mushrooms placed in the middle of the grass, unless you intend to block that path off in purpose I always think it's best to keep blocking tiles off to the sides (in this case closer to the two trees).

Keep practicing, you will naturally develop your style.