First of all, I support The Mighty Palm's approach to it.
Overgrown sounds original and better, without a doubt.
Now, if you want to reinforce that, what I'd suggest is having this "overgrown-ness" affect gameplay.
How are the enemies affected by that? Do we have plant enemies of some kind?
If there are any puzzles, why don't you make it so they fit the "overgrown" theme by having it involve vines/moss/plants in general?
Maybe you have a location blocked by plants that can be visited later?
As for mapping, I believe you could add more to the walls?
Yeah, just my opinion bits.