One of my customers (I am a pro illustrator) ask me to illustrate the cover of a book which the story is set in a hollow world. The task is new for me and not so easy.

I've try to find on the net some artworks that portrait an hollow world lanscape, but seems to be that no one do something like that before...

On yesterday I've post a test render on my Renderosity gallery with a first visual solution in order to achive my goal, receiving some interesting suggestions from Renderosity users such as lordgoron, geirla and TheBryster.
After the useful suggestions, I've changed the landscape in background.

In this new artwork have I achived to interpret a realistic lanscape (as "realistic" can it be) of an hollow world?

More suggestions (if there are) are welcome! :)