Ewww. Yeah change the ground texture to -anything- other than that. You may also want to break up a lot of the wall textures with trims they are all very samey. Also you seem to be missing a lot of the terrain that was in the original. Theres a program for making that... little java thing that I can't remember the name of. Look around on the forum theres a link somewhere.
Honestly I would say that you should remake the map completely different and from scratch. The greatwalls were never particularly great and a new and interesting take on the concept would be kinda nice. Just off the top of my head you could try mixing together nature/technology and use both grass and techy textures. Think borg assimilation thats only half way done. It would also let you use the terrain and texture blending which would make the map look a whole lot nicer.
Hey, want to learn to map? You might want to start
here and
here!