Find a file called glest.ini or glestadv.ini. Open it up and...
change the maxrenderdistance and maxcameradistance to larger numbers, such as 1024
Then play a game with your map (make sure to turn shroud and fog of war off), and zoom all the way out so you can see the whole map. Hit 'e' to take a screenshot. The resulting screenshot should be in your Glest directory in the /screens folder.
If that's too complicated for you, just take a screenshot of the map in the editor to at least give us
some idea of what to expect.
Upload your screenshot to a site like imageshack.us and paste the "forum thumbnail" link to the thread.