Some thoughts to @BlackYps ' point:
Could one option be the map title? As in, have it start with "R' for rotated symmetry and "M" for mirror or something like that?
Another option: perhaps making it create slight color variations in the terrain? Like in "Adaptive Moon" and "Moonlight Pass" where some of the ground is slightly darker. I guess it would have to be just in one area (mirror) or two areas (rotational) though; if it creates lots of areas like that it would just make it confusing.