Just some hints for you to improve your terrain:
1) watch your doodad placement. Sometimes, your doodads clip through other models or don't even reach the ground. When placing a doodad in the editor, you almost always need to move it down a little to make it hit the ground properly.
2) watch your doodad composition, especially the colors. A good terrain picture shouldn't have all colors present - always match the tinting of the doodads to the light environment. Select a "main color" for your pictures. In this case, I'd recommend a slight blue-greyish shade, as the theme is winter. Always tint your models a little bit into this color. Also, you should edit your ground textures or change the light environment to match that.
3) Remember the rules of photographing, like the golden ratio. Also, always have a focus in your pictures, meaning that there should be some emphasizis on your picture somewhere, something that draws the attention of the viewer.
4) Try to make the environment more natural. There are some rules of thumb how nature works in the world. For example, plants and trees will always come in clusters, due to the way they reproduce. The terrain also misses plants other than trees.
Also, the glaciers look misplaced; why should they be there? Glaciers exist only where there is higher ground around so that the melting water can actually accumulate. On your pictures, it almost seems like some mystical force moved them and dropped them on the flat ground.
Just some hints for you; other than that, I like the idea of the sci-fi theme.
