After reading these comments, i wanted to start anew, so i spent a couple hours on this new version, and this is what i've got so far. I think the grass is FAAAR better than it was before (i even took a colour out

), but i'm not sure about the new style of cliff. I like it fine, but... i dunno, the old one seemed more natural somehow.
Anyway, i think i addressed the lighting issue, since the cliff is more accurately shadowed on the face, and there's a shadow on the grass at the base of the cliff.
The tiles almost seem useful now as well, since there's clear "passable" or "not passable" in each. I might move the back cliff face back a bit to allow units to stand on the top face, but not underneath, since at the moment its sort of neither has room to stand on.
But i wanted to get some more feedback from you guys before i kept going in the wrong direction if the first version is better. Right now, i'm torn between the two.
Anyway, here's the old and new versions side-by-side. Any comments you have about which bits of each you like more would be greatly appreciated!
OLD --> NEW
