This is what I've done to obtain the "hollow workd effect" from a different POW. The landscape "planes" are huge in dimension. The figure was added later in Photoshop, only for reference. On the final book cover the figures (will be a couple) will be different and more fantasy. The last two upper "planes" are mapped with hi-res satellite images taken from the web. All is covered by an infinite plane mapped with clouds. As you can see, my solution is very similar to the bikermouse suggestion.

BTW: I did not find images of the inside landscape (only outside images) of the Dyson Sphere of the Star Trek episode named Relics.
Do you?