Here are some tips for terrain:
-If you are going to make raised area of land, use "Smooth" to even it out. Also, if you think it would look good, add some trees to the hill.
-Try to put as much doodads (Trees, rocks, environment stuff...) on top of cliffs to make it look more better...I think...
-If you are going to make rivers out of deep water, you should put some shallow water in some parts to put rocks and swampy plants.
-If you are going to make lakes/bays, try to surround it with trees and rocks.
-Always make paths on the land using a different tile that the units are going to follow (In rpgs, secret passages, whatever...).
-Try to make as many waterfalls as you can if you are going to use an Ashenvale, Sunken Ruins, Lordaeron Summer/Fall, or Barrens on the cliffs you make. Have them also be surrounded by trees and other doodads.
-Never leave a large area of land remain flat, try to make little hills and use "Smooth" on it.
-Do not always use trees to make walls, because they can always be destroyed and you need a flat area to place them. Use raised land or make hills with trees on top instead of just trees on a flat land.
-If you are making rivers, make sure they meet another body of large water so it won't be boring. Or if you want, try to make it on boundaries or at the end of the terrain map instead of connecting it to a lake or whatever.
If this too hard for you to understand, just let me do the terrain for you. Post your unfinished map in this website or let me just make a new map.
Ok...