We can't just say "Terrain good" and give you ideas without any sample screenshots of your terrain and then you become good all of a sudden. Please try to terrain good, when it's ready to be shown, attach a screenshot of your terrain to your post. Attaching multiple screenshots helps us help you. Supplying us with only one screenshot has a less likely of a chance for us to help you efficiently... unless it's a 64x64 map or smaller lol (Which is totally pointless IMHO)
~Craka_J
[EDIT]
Actually, here is how I started making terrain look a bit more than simple and plain:
Step1) When creating a map, it's best to start the map in "Shallow Water" instead of just a flat ground surface. This will make ponds, lakes, oceans, etc. look more realistic when created. After you've done this, you'll need to make a hill in the water and once it is finally above water enough to where you can't see water over the hill, you'll need to make it spread out all over the map with the Plateu (I think that's the name) terrain option which can be found next to hills I believe. Make the entire map just grass.
Step2) Make a patch of trees in the corner of the map.
Step3) Now select a tile that should be called "Grassy Dirt" and place Grassy Dirt only where the trees are placed. Outside of where the trees are placed should be just grass. You can also use tile called "Leaves" and use it under trees instead of Grassy Dirt.
Step4) Now to make a small pond: In terrain, click "Ditch" or the opposite of hill I guess thing and use it in the middle of the map. Doesn't have to be in the middle of the map, but let's keep it away from the trees for now. Use the ditch thing on one area of the ground (make sure you've selected a pretty big circle thing to make the ditch bigger and save you more time) and hold it until the ground has been submerged in water and you can no longer see the ocean floor.
Step5) It's probably best to use grassy dirt around the edge of the pond.
Step6) Now it's time to decorate the pond. Go in Doodads/Environment/ and then use Shrubs, Rocks, Cattalais(forgot what they're called) and place them all around the edge of the pond, but IN the water. Not outside of the water.
Step7 After it's been decorated (Make sure it doesn't look messy) you need to do pretty much one more thing: Go to Doodads/Water and place lilly pads here and there IN the pond. It's best to place River Rushes all alongside the pond as well and place lilly pads around River Rushes and Rocks. Looks more realistic if done properly.
That's how I did stuff back when I was a noob and things looked fine. Not great, but if done properly with patience, it can look alot better than a plain and simple map.
~Craka_J