First of all, Is this playable or non-playable?
I am impressed that you know how and where to use tiles properly (dirt > dirt grass > grass), other people often just put random tiles everywhere without considering proper tile transitions and call it 'a tile variety'. You also used the proper doodads in every scenes (underwater objects in the underwater scene, grassy Ashenvale scene, etc.), I also don't see unnecessary doodads so that's a good thing aswell, some of the mappers often disregard that. The only problem I see right now is the use of item chests, it doesn't feel right to be there although I understand why you put it there, better remove that. There more things to learn in terraining and you can put alot more into your scenes/terrains.
By the way, welcome to the Terrain Board!