I'm ok with making more rocks--I don't want them to become overused and repetitive, and there are only so many rotations/combinations you can use before they get old, and I don't want that. In all fairness, stage one is the 'rockiest' with the most outdoorish areas; other stages will feature both more cavey type environments and mining/wooden structures than the first. There are even a few places where the entrance of large caverns in stage two will be large rock set props--large rocky outcrops that act as an arch gateway into another area.
But my concern is filesize. Between the world textures, all new set of rocks, misc wooden props, skybox textures and whole cave environment that has yet to be made, I don't want to put any more fat into this map than there needs to be.
The comments about color and monotone are pretty legitimate concerns to me. I didn't think it was that bad, but now I can tell it's going to be a problem. I'll start using more saturated contrasting colors in places of importance, like door exits, cps, etc. And I might make a grass sprite to match the swamp grass models, I suppose it sort of depends on prop use by the end.
The last option I have, something I considered a long time was dimming the entire environment lighting and then relying on lamps/industrial lighting and self-luminous crystals to light the map. I envision this sort of solution would be the best of all--and I could probably still do some of this and it would help. at this point I just need to do it and see what happens.