Outer terrain is set to plain by default. Since your are technically editing scene 105, open up scenes.txt and search for the following line:
scn_blank_105 blank_105 256 none none 0 0 100 100 -100 0x0000000130000500400649920004406900002920000056d7 0 0 outer_terrain_plain
The bold text is of course the terrain code and will be the code you copied in, not the generic one I listed. At the end of the line, change
outer_terrain_plain to either
outer_terrain_desert if you want desert hills or
outer_terrain_desert_b if you want desert mountains.
I would also suggest keeping a backup copy of the .scn file if you are editing in the cRPG module and not a copy of the cRPG module. Repair and even patches have the potential to overwrite/erase your file and all your hard work!