Under Scenario/map options
You have a list of things you can check and uncheck.
Make certain that Use Terrain fog is checked.
Now next to that (to the right) there are various options - use linear as your style, set the start z at 900 and the end z at 9000, use a density of 0.5 select light gray as the color. click ok.
Now hit either V (to switch to game view) or just hit F (to show the fog) what you should have is a very diffuse 'white' looking fog - more of atmospheric haze than a true fog. I nearly always start off with that 'point' of my fog. From there you can modify density and color and play with the distances. In a rain setting your fog should be very light - not actually fog but a distance haze from diffuse rain.
Start z is where the fog will start closest to the camera, end z will determine where it ends furthest away from the camera. You could set end and start as something like 100 and 101 - what you end up with is a 'solid' wall or plane of solid color. The wider the distance between the two points the more diffuse the fog becomes.
Exponential - unknown, perhaps unknowable. People have asked and no one that knows has said what it does - other than make your game all that color. LOL
First image is not really a terrain image, its a closeup of some units so we really don't get anything to judge the terrain on.
Second image. More to comment on.
Trees are 'tricky' to use to make a convincing 'real' landscape.
In the wild trees are not uniform, do not come in a set range of height and size - instead in most wood land areas or clusters of trees (in the wild) there will be a few mature trees surrounded by 'seedlings' or saplings - smaller trees. single sized trees are found near and around settlements where people are busy cleaning up debris and usually remove undergrowth in the process.
The best way to use trees (even the Ashenvale trees) constructively is to make customized copies and set their height range between .1/.2 to about .8 for the game change the pathing of tree walls to barrel and of canopy tree seedings keep the same pathing. If you plan on units to harvest then lower the HP - I have found that 25 hp works rather well.
You have that lone tree standing to the far right with mushrooms around it - remove the mushrooms and use a seedling or two. You can overlap the pathing slightly by holding the shift key when placing the seedlings. Usually going at a diagonal (placing the seedling at a corner of the main tree) works rather well. For lines of trees or clusters of trees, placing a few seedlings along the long side) or just outside the cluster will give it the look of natural woodlands.. Thus your riverside line of trees should be finished off with smaller trees running right of the tree line.
Also pull in trees from other sets - such as the felwood trees and the cityscape 'cypress' type tree and the village fir, even tossing in a few dead wood trees from northrend and brown fall and dalariann ruins trees will break up the monotony and add a bit of realism to your map.
Water 'trash' works best in community/settlement settings than in the wilderness. Trash (floating debris) is expected near/in a village, in the wild we expect pristine waters. Remove the box, or give the area a good reason for human debris - a farm, a settlement (not just a camp).
Yes I know you have a camp, but it does not look like its been there long enough to have debris floating down the stream.
Rowboat - why is it in the middle of the stream/river? Put it nearer to shore this way it will not look as out of place. It will still look out of place because frankly your stream doesn't look like it can handle a rowboat or any craft - being as small as it is. Perhaps you would do best without a boat in this scene.
Cattails. Copy the rushes doodad in the object editor, tinker with the tinting - get a light green and a dark green version to go with the brown. Being selective in which version you use (DO NOT use the cattail looking rush) place in a few (very few) brown and fill in with your light green and dark green along the cattail line - this will fill in the area of the cattails, and having the greens will make it look like living rushes/reeds. If you want an autumn or winter type scene then stick with yellow and brown. you can tinker a bit more with the tinting and get sort-a kinda reddish (rust) colored ones that work rather well against snow and ice.
"I made this in about 20 minutes" Yeah and it looks like it. Sorry but terrain creation is not a race, it is not a speed based 'game', it is an art that requires careful selection of material and careful placement and some thought about what it is you are creating.
For 'natural' scenes ones must do a little image searching via Google or another search engine. Look at nature photos of landscapes, woodlands, wastelands and the like and see how Mom Nature applies her models/units to her 'game'.
Your Pluses:
You did use more than just one terrain texture ++
You did use smoothing on your shorelines ++
You did set a mood (partially) with the rain +
As a game you used an in game image ++
--> Too many people post wide vast scenes from the editor when the simple truth is that you will never see it that way in a game.
You gave some consideration to the environment by using some environmental doodads (fallen tree, mushrooms, cattails) ++
Lastly, I strongly suggest you find real images of real nature landscapes, then experiment with customized doodads, decrease/increase sizes, change the tinting, attempting to paint your landscape in a manner that looks more realistic.
