I noticed you couldn't figure out how to add the space terrain, and considering I recently had this problem and it took me awhile to figure it out, I decided to help you out.
No offense to the above posters, but that doesn't really help.
Step 1: The Skin
-Click this link, and download this skin.
-
http://www.hiveworkshop.com/forums/skins-552/outland_abyss-61045/?prev=search%3Dspace%26d%3Dlist%26r%3D20
Step 2: Assigning The Skin
-Based on what type of map terrain you are using, you will need to find a path to a type of terrain you wish to replace with the space terrain.
-Note: You will
not be able to use the selected terrain you are replacing with space. Though you can change which one it replaces later, make sure you choose one you don't need.
-Import the Space file, double click, and select the box "Use Custom Path". The custom path works as follows: TerrainArt\MapType\MapType_TerrainType.blp. For an example, I will replace "Dalaran White Marble" with the space terrain.
-To replace "Dalaran White Marble" with "Outlandobyss", you must put the imported file's custom path to TerrainArt\Dalaran\Dalaran_WhiteMarble.blp
Step 3: Seeing The Skin
-After you have important the file and changed the path with a custom one, close the Warcraft III World Editor completely (don't just close the map by hitting cntrl+w, close the entire program itself) but make sure you save your work!
-Reopen the Warcraft III World Editor and attempt to use the terrain you replaced with space. For me, it's Dalaran White Marble. When you place the terrain, it should appear as space. If this didn't work, either close the program and try again, or go to File -> Preferences and change all of the drop down colums to "High". This may create some lag, and if it does, turn it down again after. Once you hit "OK" you should then see the space terrain.
Note: There have been some instances where portions of the terrain start to overlap, so you see part of "Dalaran White Marble" and "Outlandobyss" mixed together. This is caused by the fact that not a lot of time was actually spent designing this program, and some bugs still exist. Simply close the program and reopen it until the error fixes itself.
Step 4: Enjoy Your Map!

-If you followed my steps you should be able to use the terrain as specified, though some problems could arise. Contact me at
[email protected] if you have any questions, or simply send me a personal message.
Good Luck.