Nice green enviro, i'd bear in mind the scale of the man in the background, that'd make those very narrow tunnels. The piece is nice but i feel it's a bit too middling, I'd agree with dan and start adjusting your hues, maybe make the shadows a bit orange. It'll help to add depth. Also don't be afraid to take all your brush adjustments off and work hard for a few edges, really helps to define them. Maybe an orange glow on the creatures glowy bit... the scientific name obviously.
Nice model! Very true to the original concept!