Looks good so far! I'll second some of the comments I've seen in the thread - for example, the rock texture should be horizontal (sedimentary rock forms in layers vertically.

), you might want to find another wood texture, etc. I think I recall you saying some of that was in the works.
I think you really should emphasize the level-over-level here, otherwise it will get far too linear. You get some variation in that third shot, but try to keep extra routes above and below to keep things interesting - 3 or even 4 layers could make for some insane vertical combat. Keep up the good work